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Consequences of electromagnetic field (EMF) radiation during early pregnancy - Androgen synthesis and release from the myometrium of pigs in vitro
Abstract
An electromagnetic field (EMF) has been found to affect reproductive processes in females. The aim of this study was to determine the effect of low, non-ionizing EMF radiation on the steroidogenic activity of myometrium collected from pigs during the fetal peri-implantation period. Myometrial slices were treated with an EMF (50 and 120 Hz, 2 and 4 h of incubation) and examined for the aromatase cytochrome P450 17α-hydroxylase/C17-20lyase (CYP17A1) and 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (HSD3B1) mRNA transcript abundance, cytochrome P450c17 and 3βHSD protein abundance and the secretion of androstenedione (A4) and testosterone (T). To determine whether progesterone (P4) functions as a protectant from EMF radiation, the selected slices were treated with P4. In slices incubated without P4, EMF at 50 Hz altered cytochrome P450c17 protein abundance (4 h), HSD3B1 mRNA transcript abundance (4 h) and A4 release (2 h) as well as T release (2 h) in P4-treated slices. The EMF at 120 Hz in non P4-treated slices altered A4 release (2 and 4 h) whereas in P4-treated slices altered CYP17A1 mRNA transcript abundance (4 h), 3βHSD protein abundance (4 h), A4 (4 h) and T release (2 h). In conclusion, EMF radiation in the myometrium collected during the peri-implantation period alters the CYP17A1 and HSD3B1 mRNA transcript and encoded protein abundance, and androgen release due to the time of treatment and P4 presence or absence. The P4 did not function directly as an obvious protector against EMF radiation in the myometrium of pigs during the fetal peri-implantation period.
... As a result, Electric Energy (EEIX) and magnetic energy propagate to space through EMW with the periodic transformation of EF and MF [8][9][10]. The EMW is a shear wave, and the MF, EF, and traveling direction of the EMW are perpendicular to one another [11][12][13]. The propagation of EMW includes ground waves propagating and airwaves propagating. ...
... Equations (9) and (10) suggest that the VMP and ESP are related to the four theorems in Section 2.1 and, thus, can be applied to them. The specific forms are shown in Equations (11) and (12). ...
... In Equation (12), the letters share the same meaning as those in the above equations. ...
In order to deeply analyze the performance of Electromagnetic Field (EMF) on wireless sensor Signal Processing (SP), this paper first examines the influencing factors of wireless sensor SP performance based on the relevant theories of EMF and wireless sensor. Then, it discusses the influence of EMF on wireless sensor information Transmission and Reception (T & R) time, Package Reception Rate (PRR), and communication throughput. Furthermore, the Packet Loss Rate (PLR) and Bit Error Rate (BER) of the sensor are described, and finally, a conclusion is drawn. The research findings are as follows. This paper makes a statistical study on whether the wireless sensor is disturbed by EMI from three aspects (wireless sensor’s information T & R time, PLR, and communication throughput). In any case, EMF will prolong the wireless sensor’s information T & R time and reduce the PRR and communication throughput. When the distance between the transmitter and the receiver is set to 5 m, the change of field intensity at the transmitter significantly impacts the BER but has little impact on the PLR. However, when the field intensity of the transmitter and the receiver is the same, PLR and BER show no evident difference. Therefore, this paper studies the SP performance of the wireless sensor in the EMI environment, which provides an excellent reference significance for the rapid development of wireless sensors in the future.
... Previous studies provided shreds of evidence that the exposition to the EMFs affects the reproductive processes in mammals [2,4,[6][7][8]. In females, the EMF radiation altered the course and length of the estrous cycle, ovulation and conception rate, the dynamics of fetal growth, and pregnancy outcome [2,4,6]. Nevertheless, the molecular background of these changes is hardly understood. ...
... Nevertheless, the molecular background of these changes is hardly understood. Due to the fact that the success of early pregnancy is ensured by a unique embryo-maternal dialog involving the action of steroid hormones [9,10], it was proposed that jeopardizing effects of the EMF treatment on pregnancy development might be coupled with the altered uterine steroidogenic activity [7,8,11,12]. Indeed, recent in vitro studies on a pig model demonstrated that the EMF treatment (50 and 120 Hz, 8 mT, 2 and 4 h) induces alterations in the synthesis and secretion of steroid hormones by the uterine tissues, including the myometrium [7,8,11,12]. ...
... Due to the fact that the success of early pregnancy is ensured by a unique embryo-maternal dialog involving the action of steroid hormones [9,10], it was proposed that jeopardizing effects of the EMF treatment on pregnancy development might be coupled with the altered uterine steroidogenic activity [7,8,11,12]. Indeed, recent in vitro studies on a pig model demonstrated that the EMF treatment (50 and 120 Hz, 8 mT, 2 and 4 h) induces alterations in the synthesis and secretion of steroid hormones by the uterine tissues, including the myometrium [7,8,11,12]. Notably, in pigs, the myometrium contributes significantly to the total uterine production of androstenedione (A4) [13], which induces anabolic processes in the target tissues and regulates morphogenesis, cellular proliferation, and hyperplasia [14]. ...
The electromagnetic field (EMF) affects the physiological processes in mammals, but the molecular background of the observed alterations remains not well established. In this study was tested the effect of short duration (2 h) of the EMF treatment (50 Hz, 8 mT) on global transcriptomic alterations in the myometrium of pigs during the peri-implantation period using next-generation sequencing. As a result, the EMF treatment affected the expression of 215 transcript active regions (TARs), and among them, the assigned gene protein-coding biotype possessed 90 ones (differentially expressed genes, DEGs), categorized mostly to gene ontology terms connected with defense and immune responses, and secretion and export. Evaluated DEGs enrich the KEGG TNF signaling pathway, and regulation of IFNA signaling and interferon-alpha/beta signaling REACTOME pathways. There were evaluated 12 differentially expressed long non-coding RNAs (DE-lnc-RNAs) and 182 predicted single nucleotide variants (SNVs) substitutions within RNA editing sites. In conclusion, the EMF treatment in the myometrium collected during the peri-implantation period affects the expression of genes involved in defense and immune responses. The study also gives new insight into the mechanisms of the EMF action in the regulation of the transcriptomic profile through lnc-RNAs and SNVs.
... Importantly, a pivotal source of estrogens in the uterus is the endometrium and the myometrium, in which steroidogenic activity depends on the reproductive status of the female [6][7][8]. Interestingly, past studies indicated that uterine steroidogenic activity might also be regulated not only by endocrine factors [9][10][11][12][13][14][15][16][17], but also by physical environmental factors, such as an electromagnetic field (EMF) [18][19][20]. ...
... In estrous-cyclic pigs, during the mid-luteal phase of the estrous cycle, an EMF at a frequency of 50 and 120 Hz increased myometrial estradiol-17β (E 2 ) release within 4 h of treatment duration [18]. It was also determined that treatment with an EMF (50 Hz for 2 h, 120 Hz for 2 and 4 h) decreases the myometrial release of androstenedione (A 4 ) [19]. Table 1. ...
... The mechanism of steroid production is determined by cytochrome P450 17α-hydroxylase/C17-20 lyase (cytochrome P450c17), which is a rate-limiting enzyme controlling the entry of P 4 and pregnenolone to the steroidogenic pathway [27,36]. Previously, it was documented that a longer (4 h) treatment duration of the EMF at a frequency of 50 Hz results in a greater cytochrome P450c17 protein abundance, but did not affect A 4 release by the myometrium collected from pigs during the peri-implantation period [19]. The EMF radiation at a higher (i.e., 120 Hz) frequency led to an increased concentration of myometrial A 4 when there was the inclusion of P 4 in the culture medium within a longer (4 h) treatment duration of EMF, which coincided with the greater 3β hydroxysteroid dehydrogenase (3βHSD) abundance in the tissue [19]. ...
An electromagnetic field (EMF) may affect the functions of uterine tissues. This study hypothesized that EMF changes the estrogenic activity of pig myometrium during the peri-implantation period. Tissue was collected on days 15–16 of the gestation and incubated in the presence of EMF (50 and 120 Hz, 2 and 4 h). The cytochrome P450 aromatase type 3 (CYP19A3) and hydroxysteroid 17β dehydrogenase type 4 (HSD17B4) mRNA transcript abundance, cytochrome P450arom (aromatase), and 17β hydroxysteroid dehydrogenase 17βHSD) protein abundance and estrone (E1) and estradiol-17β (E2) release were examined using Real-Time PCR, Western blot and radioimmunoassay. Selected myometrial slices were treated with progesterone (P4) to determine whether it functions as a protector against EMF. CYP19A3 mRNA transcript abundance in slices treated with EMF was less at 50 Hz (2 h) and greater at 120 Hz (2 and 4 h). HSD17B4 mRNA transcript was greater in slices treated with EMF at 120 Hz (2 h). Progesterone diminished EMF-related effects on CYP19A3 and HSD17B4. When P4 was added, EMF had suppressive (50 and 120 Hz, 2 h) or enhancing (50 Hz, 4 h) effects on aromatase abundance. The E1 release was lower after 4 h of EMF treatment at 50 Hz and P4 did not protect myometrial E1 release. In conclusion, EMF alters the synthesis and release of E1 and did not affect E2 release in the myometrium during the peri-implantation period.
... There are aberrant steroidogenic actions, as a consequence of low-frequency EMF radiation, in the endometrium and myometrium of pigs during the mid-luteal phase of the estrous cycle (Koziorowska et al., 2018) and myometrium of pigs during the fetal peri-implantation period (Franczak et al., 2020). Progesterone (P 4 ), which functions as a substrate for the synthesis of steroid hormones in the uterus (Franczak, 2008;Kotwica, 2008, 2010), may function as a factor protecting against EMF radiation in estrous cyclic females (Koziorowska et al., 2018), but protective functions of this hormone during the early gestation period has not been evaluated. ...
... The functions of the endometrium, are essential for embryo-uterine interactions during the fetal peri-implantation period (Ziecik et al., 2006;Waclawik et al., 2017). In the pig uterus, steroid 17αhydroxylase/17, 20-lyase (cytochrome P450c17, encoded by CYP17A1), hydroxyΔ5steroid dehydrogenase/3β and steroidΔisomerase (3βHSD, encoded by HSD3B1) are essential for ensuring uterine steroidogenesis, including androgen production (Spencer et al., 2004;Kotwica, 2008, 2010;Wojciechowicz et al., 2013;Franczak et al., 2020). ...
... Endometrial slices were placed in 24-well culture plates and covered with pre-incubation medium (1 mL, M199, Sigma Aldrich, St. Louis, MO, USA, 0.1 % BSA, Carl Roth GmBH + Co KG, Mühlburg, Karlsruhe, Germany, 1% antibioticantimycotic solution) and then pre-incubated for 2 h in 37 • C, 95 % O 2 and 5 % CO 2 in a water-shaking bath, as previously described (Koziorowska et al., 2018;Franczak et al., 2020). After pre-incubation, the culture media were discarded and replaced with the fresh media. ...
An electromagnetic field (EMF) may have effects on female reproduction. This study was conducted to determine whether EMF [50 and 120 Hz, 2 and 4 h of incubation in the presence or absence of progesterone (P4, 10⁻⁵ M)] affects androgen synthesis and release from the pig endometrium. Endometrial slices were collected from pigs (n = 5) during the fetal peri-implantation period (i.e., days 15–16 of gestation) and treated in vitro with EMF. The selected endometrial slices were treated with P4 to determine whether this hormone has effects on protection of the tissue from EMF radiation. The CYP17A1 and HSD3B1 mRNA transcript abundance, steroid 17αhydroxylase/17, 20-lyase (cytochrome P450c17) and hydroxyΔ5steroid dehydrogenase/3β and steroidΔisomerase (3βHSD) protein abundance were examined using Real-Time PCR and Western Blot procedures, respectively. In media collected after incubation, the concentrations of androstenedione (A4) and testosterone (T) were quantified used a RIA. When P4 was added to the culture medium, EMF radiation had suppressive effects on endometrial T release after 2 and 4 h of incubation when the EMF treatment was occurring and increased A4 release after 4 h of incubation with EMF at 120 Hz. When there was no inclusion of P4, release of A4 was decreased after 2 h of EMF treatment at 120 Hz and after 4 h of EMF treatment at 50 and 120 Hz. Progesterone did not have functions that protected the pig endometrium against EMF radiation during the fetal peri-implantation period.
... High phone usage is compounded by frequent charging, with 43.1% of respondents charging their devices daily, and 35.4% charging multiple times a day, indicating a pattern of digital dependence and sustained EMR exposure. 46.5% report dizziness and fatigue, and 39.5% suffer from nausea. These symptoms suggest a direct correlation between mobile phone use and physiological stress, further exacerbating health risks related to reproductive function. ...
... In addressing this gap, our survey offers novel data on menstrual health within the context of EMR exposure among young adult women. The prevalence of fatigue, stress, and irregular cycles among high phone usage participants not only supports existing studies, such as Bakacak et al. (2015) [46] which documented EMRinduced reductions in ovarian follicles-but also propels the conversation forward, connecting these biological impacts with specific behavioural patterns. Furthermore, the psychological implications of EMR, including increased stress and anxiety, align with studies like Yüksel et al. (2016) [47], which document oxidative stress in EMR-exposed offspring, thereby expanding the dialogue on EMR's potential psychological influences. ...
The purpose of this study is to investigate the presence of non-ionizing radiation and its effect on female reproductive health, particularly in India. The issue of non-ionizing radiation is especially relevant in India, a rapidly modernizing nation, as its society adapts to advancements in technology and infrastructure development. Of particular interest to us are the biological effects of non-ionizing radiation on women of reproductive age. Consequently, we aim to determine whether women perceive non-ionizing radiation in their environment or living spaces, and ascertain whether any complaints related to the reproductive system are more frequent when the respondents believe non-ionizing radiation is present, in addition to discussing possible mechanisms and outcomes from previously conducted research. Despite a general lack of awareness about non-ionizing radiation in India and its potential impact, it is anticipated that women are exposed to this type of radiation, either through close contact with emitting devices or relay towers installed near residential areas. We also expect that some symptoms related to the reproductive system, as reported by women, will become more prevalent when nonionizing radiation is present
... Although it was concluded that the health impact of the ELF-EMF may be regarded as being relatively low [4], the ELF-EMF strength may be sufficient to affect biological functions [4,5]. It was demonstrated that the ELF-EMF induces changes in transcriptomic profile [7,8], DNA methylation level [9,10], the abundance of epigenetic-regulation-related factors [11], and steroidogenesis [12][13][14][15] in porcine endometrium and myometrium in vitro. Remarkably, it was also found that the ELF-EMF may evoke changes in apoptosis and oxidative stress in various mammalian cell types, i.e., human leukemia cell line K562, endothelial cells, HeLa cells, and mouse macrophages [16][17][18][19]. ...
... The endometrial slices were exposed for two hours to constant, sinusoidal ELF-EMF at a frequency of 50 Hz and magnetic field of 8 × 10 4 mG using the ELF-EMF generator (Magneris device-Astar; https://www.astar.pl/produkty/magneris; accessed on 20 May 2017) as described previously [8,9,12,103]. The generator was equipped with flat applicators, by which sinusoidal, triangular, or rectangular waveforms of ELF-EMF can be emitted with frequencies ranging from 2 to 120 Hz [104]. ...
Nowadays, the extremely-low-frequency electromagnetic field (ELF-EMF) is recognized as environmental pollution. The data indicate that the ELF-EMF may affect factors related to epigenetic regulation and alter important biological processes in the uterus. The impact of the ELF-EMF on apoptosis and oxidative-stress-related genes has not been documented in porcine endometrium. This raises the question of whether the exposure to the ELF-EMF can induce apoptosis and/or oxidative stress in the endometrium of pigs during the peri-implantation period. Porcine endometrial slices (100 ± 5 mg) collected (n = 5) during the peri-implantation period were treated in vitro with ELF-EMF at a frequency of 50 Hz and flux density of 8 × 104 mG for 2 h. To determine the effect of ELF-EMF on apoptosis and oxidative stress in the endometrium, CASP3, CASP7, CIDEB, GADD45G, NOS1, NOS2, NOS3, and TP53I3 mRNA transcript were analyzed using real-time PCR, and protein abundance of CASP3, CASP7 using Western blot, and eNOS using ELISA were determined. Moreover, CASP3/7 and NOS activity was analyzed using flow cytometry and colorimetry, respectively. The decreased CASP7 and increased NOS3 mRNA transcript and protein abundance in ELF-EMF-treated endometrium were observed. Moreover, CIDEB, GADD45G, and TP53I3 mRNA transcript abundance was increased. Only p ≤ 0.05 was considered a statistically significant difference. The documented alterations indicate the potential of the ELF-EMF to affect apoptosis and generate oxidative stress in the endometrium. The insight into observed consequences documents for the first time the fact that the ELF-EMF may influence endometrial cell proliferation, angiogenesis, and/or tissue receptivity during peri-implantation.
... Furthermore, exposure to EMF of 50 Hz generates a high stress index in mice, provoking changes in their social behavior (Vera and Muñoz, 2020). Franczak et al. (2020) reported reproductive problems in pigs after installing a cellular telephone base station nearby. The number of litters and piglets has decreased considerably and the number of malformations has increased (Franczak et al., 2020). ...
... Franczak et al. (2020) reported reproductive problems in pigs after installing a cellular telephone base station nearby. The number of litters and piglets has decreased considerably and the number of malformations has increased (Franczak et al., 2020). According to Wiltschko and Wiltschko (2005), if cows are exposed to 40 Hz electromagnetic fields, they produce less milk, their wool becomes soft and they may even have infertility. ...
... 16 Given the widespread and continuous use of technology that emits EMF-r, it is essential to understand the long-term effects of EMF-r exposure on human health and the environment. 17 However, most of the studies conducted on exposure of EMF-r to plants are of short-term in nature. Moreover, study on EMF-r exposure to wheat crop growth, ecophysiology and carbohydrate metabolism is limited. ...
In recent decades, the widespread adoption of wireless electronic devices, notably cell phones, has led to a considerable rise in environmental electromagnetic field radiations (EMF‒r). The EMF-r has potential to interact and interfere with the living organisms. Therefore, it is essential to examine how these radiations affect biological systems, including plants which are immobile in nature and may remain continuously exposed to these radiations. The present study investigated the long-term exposure effects of 2850 MHz EMF‒r on 30 and 60‒days old wheat (Triticum aestivam L.) crop, focusing on their growth, photosynthetic pigments, and carbohydrate metabolism. The findings of the study revealed that the EMF‒r exposure leads to a decline in root length, shoot length, and plant biomass along with a marked reduction in photosynthetic pigments. Moreover, a significant reduction in carbohydrate‒metabolizing enzyme activity, water‒soluble carbohydrate, and reducing sugars content was observed in EMF‒r irradiated samples. The study suggests that EMF‒r exposure adversely affects the plant growth, photosynthetic pigments, and carbohydrate metabolism, highlighting the need for effective management to prevent productivity losses.
... The speed of the method is also important: testing of a single series of samples can be performed in 2-3 hours. The use of this method to determine the protection properties of biotextile against electromagnetic fields is based on knowledge that UV-B and LF-EMF radiation are known to be cell stress factors that can affect cellular processes (Karim et al., 2012;Peykarestan et al., 2012;Franczak et al., 2020) including damage to DNA resulting in heritable mutations, and damage leading to disturbance of cell physiological processes. ...
An established biotesting system designed to discover specific features of innovative multifunctional biotextile, encompassing integrated silica dioxide and succinite (Baltic amber) particles, is founded on reproducible, reliable, and relatively fast methods. The main idea starting this study was to create a system of test methods devoted to identification of specific features of biotextile materials designed to preserve living organisms from adverse environmental factors like enhanced electromagnetic radiation of different frequencies, without use of vivarium animals. Cultures of the freshwater macrophyte duckweed ( Lemna minor ) line Sta2 and fruit flies ( Drosophila melanogaster ) were chosen as model systems suitable for the study of the influence of electromagnetic field (EMF) radiation. The experiments showed changes of phenotypic features and growth parameters of test objects, as well as induction of point mutations of DNA (for example, insertions or deletions in chloroplast DNA and nucleotide substitutions in nuclear genes). The responses of test organisms induced by EMF were studied using microscopy, flow cytometry, and DNA sequencing methods. On the cell level, a new fast flow cytometry method for biotextile testing was developed: immature gametic (pollen) cell cultures were used as a highly sensitive model system (plant gametic cell response is comparable to human neutrophil response) to study the influence of EMF radiation. The method was based on the measurement of differences of fluorescence intensity between group of cells experimentally affected by EMF radiation and non-affected cells.
... However, the effect on reactive oxygen species (ROS) level was found contrasting as exposure at 850 MHz, and 1.8 GHz in human spermatozoa showed significant rise in reactive oxygen species and DNA fragmentation with the decrease in motility and viability of sperm ( Fig. 2) [59,61,62] while according to a recent study, mouse Leydig cells when treated with radiations of 1950 MHz frequency and SAR 3 W/kg for 24 h, showed deregulation of the cell cycle with reduced proliferation and testosterone secretion but with negligible effect on ROS and cellular apoptosis [64]. Androgens have a vital role in maintaining fertility, but RF exposed mice Leydig cells and pig myometrium showed decreased androgen synthesis and secretion, thus affecting fertility [64,65]. Apart from these studies, a recent study on mice spermatozoa indicated complex III of respiratory chain in mitochondria as the key target of Electromagnetic Radiation, which after Table 1 In vitro studies on the effect of RF-EMR on the male reproductive system. ...
Radiofrequency exposure from man-made sources has increased drastically with the era of advanced technology. People could not escape from such RF radiations as they have become the essential part of our routine life such as Wi-Fi, microwave ovens, TV, mobile phones, etc. Although non-ionizing radiations are less damaging than ionizing radiations but its long term exposure effect cannot be avoided. For fertility to be affected, either there is an alteration in germ cell, or its nourishing environment, and RF affects both the parameters subsequently, leading to infertility. This review with the help of in vitro and in vivo studies shows that RF could change the morphology and physiology of germ cells with affected spermatogenesis, motility and reduced concentration of male gametes. RF also results in genetic and hormonal changes. In addition, the contribution of oxidative stress and protein kinase complex after RFR exposure is also summarized which could also be the possible mechanism for reduction in sperm parameters. Further, some preventative measures are described which could help in reverting the radiofrequency effects on germ cells.
Context:
Extremely low-frequency electromagnetic field (ELF-EMF) emission is increasing due to substantial technological progress. The results of previous research provided evidence that ELF-EMF may exert changes in molecular mechanisms that control female reproduction.
Aims:
We hypothesised that short-term ELF-EMF treatment alters the DNA methylation level of genes in the endometrium. Hence, the research aimed to determine the methylation level of selected genes whose expression was altered in response to ELF-EMF radiation in the endometrium of pigs during the peri-implantation period (days 15-16 of pregnancy).
Methods:
Porcine endometrial slices (100±5mg) were collected during the peri-implantation period and exposed to ELF-EMF at a frequency of 50Hz for 2h in vitro. The control endometrium was not exposed to ELF-EMF. The level of DNA methylation in the promoter regions of EGR2, HSD17B2, ID2, IL1RAP, MRAP2, NOS3, PTGER4, SERPINE1, VDR and ZFP57 was tested using qMS-PCR.
Key results:
In the endometrium exposed to ELF-EMF, the level of methylation of HSD17B2, MRAP2, SERPINE1, VDR and ZFP57 was not altered; the level of methylation of EGR2, ID2 and PTGER4 increased, and the level of methylation of IL1RAP and NOS3 decreased.
Conclusions:
ELF-EMF may alter the level of DNA methylation in the endometrium during the peri-implantation period.
Implications:
Changes in the DNA methylation induced by ELF-EMF may affect the transcriptomic profile of the endometrium and disturb physiological processes accompanying implantation and embryo development.
Previous research by the authors indicated that an extremely low-frequency electromagnetic field (ELF-EMF) evokes molecular alterations in the porcine myometrium. It was hypothesized that the ELF-EMF could induce alterations in the epigenetic regulation of gene expression in the myometrium. In the current study, slices of the porcine myometrium during the peri-implantation period (n = 4) were used for further in vitro exposition to ELF-EMF (50 Hz, 8 mT, 2 h treatment duration). The study tested whether the ELF-EMF may affect: 1/the expression of DNA (cytosine-5)-methyltransferase 1 (DNMT1) and DNA (cytosine-5)-methyltransferase 3a (DNMT3a), 2/the level of genomic DNA methylation, and 3/the level of amplification of methylated and unmethylated variants of promoter regions of selected genes with altered expression in response to ELF-EMF. It was found that ELF-EMF treatment increased DNMT1, decreased DNMT3a mRNA transcript and protein abundance, and increased the level of genomic DNA methylation. The direction of alterations in the level of amplification of methylated and unmethylated variants of the promoter region of selected genes with altered expression, i.e. prodynorphin (PDYN), interleukin 15 (IL15) signal transducer and activator of transcription 5A (STAT5A), tumor necrosis factor (TNF), and between down-regulated genes were early growth response 2 (EGR2), hyaluronan and proteoglycan link protein 1 (HAPLN1), and uteroferrin associated basic protein-2 (UABP2), mostly involving the direction of changes in their transcriptional activity, which was evaluated in a previous study by the authors. Thus, ELF-EMF radiation disturbs epigenetic mechanisms, which may underlay ELF-EMF-related transcriptomic alterations in the myometrium.
By growing the electrical power networks and electronic devices, electromagnetic fields (EMF) have become an inseparable part of the modern world. Considering the inevitable exposure to a various range of EMFs, especially at extremely low frequencies (ELF-EMF), investigating the biological effects of ELF-EMFs on biological systems became a global issue. The possible adverse consequences of these exposures were studied, along with their potential therapeutic capabilities. Also, their biological impacts in combination with other chemical and physical agents, specifically ionizing radiation (IR), as a co-carcinogen or as adjuvant therapy in combination with radiotherapy were explored. Here, we review the results of several in-vitro and in-vivo studies and discuss some proposed possible mechanisms of ELF-EMFs' actions in combination with IR. The results of these experiments could be fruitful to develop more precise safety standards for environmental ELF-EMFs exposures. Furthermore, it could evaluate the therapeutic capacities of ELF-EMFs alone or as an improver of radiotherapy.
Context:
Electrical devices and power systems are the sources of EM-waves which propagate everywhere in the environment.
Aims:
The study aimed to determine whether EMF induced changes in the steroidogenesis of conceptuses and whether progesterone (P4) may be a possible protectant against the effects of EMF radiation.
Methods:
The entire porcine conceptuses were collected during the peri-implantation period (days 15-16 of pregnancy), divided into fragments (100mg) and treated in vitro with EMF (50Hz or 120Hz, 2 or 4h exposure), and examined to determine of CYP17A1, HSD3B1, CYP19A3, and HSD17B4 mRNA transcript and encoded protein abundance and the release of steroid hormones. Selected fragments of conceptuses were treated with P4.
Key results:
In conceptuses incubated without P4, EMF at 120Hz decreased androstenedione (A4) and testosterone (T) release after 2h and increased oestrone (E1) release at 50Hz and 120Hz after 4h exposure. In P4-treated conceptuses, EMF (50 and 120Hz, 4h exposure) decreased CYP19A3 mRNA transcript abundance, and increased (120Hz, 2h exposure) oestradiol-17β (E2) release.
Conclusions:
The EMF radiation alters androgen and oestrogen synthesis and release from the conceptuses of pigs during the peri-implantation period. The P4 exerts protective effects on androgens and E1 release but it sensitises the conceptuses when comes to the mechanism of oestrogen synthesis and release during EMF radiation.
Implications:
The effect of EMF radiation on the steroidogenic pathway in conceptuses may induce disturbances in their proper development and implantation.
The electromagnetic field (EMF) is an environmental risk factor that may impair living organisms. This study aims to determine the functional effects of EMF exposure at 50 and 120 Hz for 2 or 4 h on estrogen synthesis and release in the endometrium. Endometrial slices were isolated from pigs (n = 5) during the peri-implantation period. To check whether progesterone (P4) exerts any protective effects against EMF, selected EMF-treated slices were also treated with P4. CYP19A3 mRNA transcript abundance was higher in slices exposed to EMF (50 Hz, 4 h) and treated with P4. HSD17B4 mRNA transcript abundance was higher in slices exposed to EMF (50 and 120 Hz, 2 h) without P4 treatment. Both EMF (50 Hz, 2 h) and EMF (50 and 120 Hz, 4 h) increased HSD17B4 mRNA transcript abundance in the presence of P4; EMF (120 Hz, 2 h, and 50 Hz, 4 h) decreased cytochrome P-450arom protein abundance in tissue slices not treated with P4. Under exposure to EMF at 120 Hz (2 h), the abundance of hydroxysteroid 17β dehydrogenase decreased in P4-treated slices and increased in slices not treated with P4 (4 h). Progesterone treatment decreased the release of estradiol-17β (E2) in endometrial slices exposed to EMF at 50 Hz (2 h), whereas in slices not treated with P4, EMF (120 Hz, 2 h) increased estrone (E1) release compared to control (without EMF). The EMF could disrupt the synthesis and release of E1 and E2 by the porcine endometrium during the peri-implantation period.
A low-frequency electromagnetic field (EMF) is an environmental pollutant that may influence female reproduction. This research was undertaken to test the hypothesis that EMF causes alterations in the transcriptomic profile of the endometrium. This study investigated the in vitro effects of EMF treatment (50 Hz, 2 h) on global transcriptome alterations in the endometrium isolated from pigs during the peri-implantation period. The control endometrium was not treated with EMF. The EMF treatment altered the expression of 1561 transcriptionally active regions (TARs) in the endometrium. In the group of 461 evaluated DEGs, 156 were up-regulated (34%), 305 were down-regulated (66%) and 341 (74%) had known biological functions. A total of 210 long noncoding RNAs (lncRNAs) with changes in expression profiles, and 146 predicted RNA editing sites were also evaluated. Exposure to EMF changes the expression of genes encoding proteins that are involved in proliferation and metabolism in endometrial tissue. These results provide useful inputs for further research into the impact of EMF on molecular changes in the uterus during the peri-implantation period and, consequently, pregnancy outcome.
This article presents a review of the published scientific studies on the potential adverse effects of power frequency electromagnetic field (50-60 Hz) from domestic and occupational sources and electric transmission lines on female reproduction system and pregnancy outcome. In this review, publications in English were searched in the ISI Web of Knowledge, PubMed databases and Google Scholar from January 2000 to December 2017 articles. For ascertaining the reliability of study, data were extracted independently and in duplicate by two investigators. According to some of the conducted studies, environmental exposure to power frequency EMF (electromagnetic field) exposure was found to adversely affect sex hormones, female genital system, embryonic development, pregnancy outcome and fetal and offspring development, while other studies reported no significant effect of power frequency EMF exposure on reproductive parameters and embryonic and fetal development. Overall, the results were not convergent and there was controversy regarding the findings. However, it can be concluded that a part of controversy can be attributed to differences in field strength and exposure time, the experiment condition in terms of in vivo and in vitro which had a significant impact on the observed results.
We aimed to review the findings of exposure assessment studies done in European countries on the exposure of the general public to low frequency electric and magnetic fields (EMFs) of various frequencies. The study shows that outdoor average extremely low frequency magnetic fields (ELF-MF) in public areas in urban environments range between 0.05 and 0.2 µT in terms of flux densities, but stronger values (of the order of a few µT) may occur directly beneath high-voltage power lines, at the walls of transformer buildings, and at the boundary fences of substations. In the indoor environment, high values have been measured close to several domestic appliances (up to the mT range), some of which are held close to the body, e.g., hair dryers, electric shavers. Common sources of exposure to intermediate frequencies (IF) include induction cookers, compact fluorescent lamps, inductive charging systems for electric cars and security or anti-theft devices. No systematic measurement surveys or personal exposimetry data for the IF range have been carried out and only a few reports on measurements of EMFs around such devices are mentioned. According to the available European exposure assessment studies, three population exposure categories were classified by the authors regarding the possible future risk analysis. This classification should be considered a crucial advancement for exposure assessment, which is a mandatory step in any future health risk assessment of EMFs exposure.
BACKGROUND
Understanding the physiology of pregnancy enables effective management of pregnancy complications that could otherwise be life threatening for both mother and fetus. A functional uterus (i) retains the fetus in utero during pregnancy without initiating stretch-induced contractions and (ii) is able to dilate the cervix and contract the myometrium at term to deliver the fetus. The onset of labour is associated with successful cervical remodelling and contraction of myometrium, arising from concomitant activation of uterine immune and endocrine systems. A large body of evidence suggests that actions of local steroid hormones may drive changes occurring in the uterine microenvironment at term. Although there have been a number of studies considering the potential role(s) played by progesterone and estrogen at the time of parturition, the bio-availability and effects of androgens during pregnancy have received less scrutiny. The aim of this review is to highlight potential roles of androgens in the biology of pregnancy and parturition.METHODSA review of published literature was performed to address (i) androgen concentrations, including biosynthesis and clearance, in maternal and fetal compartments throughout gestation, (ii) associations of androgen concentrations with adverse pregnancy outcomes, (iii) the role of androgens in the physiology of cervical remodelling and finally (iv) the role of androgens in the physiology of myometrial function including any impact on contractility.RESULTSSome, but not all, androgens increase throughout gestation in maternal circulation. The effects of this increase are not fully understood; however, evidence suggests that increased androgens might regulate key processes during pregnancy and parturition. For example, androgens are believed to be critical for cervical remodelling at term, in particular cervical ripening, via regulation of cervical collagen fibril organization. Additionally, a number of studies highlight potential roles for androgens in myometrial relaxation via non-genomic, AR-independent pathways critical for the pregnancy reaching term. Understanding of the molecular events leading to myometrial relaxation is an important step towards development of novel targeted tocolytic drugs.CONCLUSIONS
The increase in androgen levels throughout gestation is likely to be important for establishment and maintenance of pregnancy and initiation of parturition. Further investigation of the underlying mechanisms of androgen action on cervical remodelling and myometrial contractility is needed. The insights gained may facilitate the development of new therapeutic approaches to manage pregnancy complications such as preterm birth.
Steroid hormones are produced by the porcine uterus. We hypothesized that the uterus in pigs possesses active 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4) isomerase (3β-HSD) responsible for progesterone and androstenedione production, that uterine steroids may supplement the amount of steroid hormones produced by embryos and corpus luteum and that these steroids are necessary for maintenance of pregnancy. In this study, we examined 1) endometrial and myometrial expression of 3β-HSD mRNA, 2) uterine 3β-HSD protein activity and 3) in vitro production of A(4) and P(4) by uterine slices harvested from pigs on days 10 to 11, 12 to 13 and 15 to 16 of pregnancy and the estrous cycle. The expression of 3β-HSD and the presence and activity of 3β-HSD protein were different in the endometrium and the myometrium during the examined periods of pregnancy and the estrous cycle. Production of A(4) by the endometrium and myometrium was highest on days 12 to 13 of pregnancy and the estrous cycle. Endometrial secretion of P(4) did not differ in the course of early pregnancy and on the respective days of the estrous cycle. The gravid myometrium was the highest source of P(4) in pregnant pigs on days 12 to 13. The release of P(4) by the cyclic myometrium rose during the examined days of the estrous cycle. The steroidogenic activity of the uterus, as described in this study, may support early pregnancy or the luteal phase of the estrous cycle in pigs.
The safety of human exposure to an ever-increasing number and diversity of electromagnetic field (EMF) sources both at work and at home has become a public health issue. To date, many in vivo and in vitro studies have revealed that EMF exposure can alter cellular homeostasis, endocrine function, reproductive function, and fetal development in animal systems. Reproductive parameters reported to be altered by EMF exposure include male germ cell death, the estrous cycle, reproductive endocrine hormones, reproductive organ weights, sperm motility, early embryonic development, and pregnancy success. At the cellular level, an increase in free radicals and [Ca(2+)]i may mediate the effect of EMFs and lead to cell growth inhibition, protein misfolding, and DNA breaks. The effect of EMF exposure on reproductive function differs according to frequency and wave, strength (energy), and duration of exposure. In the present review, the effects of EMFs on reproductive function are summarized according to the types of EMF, wave type, strength, and duration of exposure at cellular and organism levels.
SUMMARY Conceptus (placental membranes, fetal fluids and fetus) development in intact control (IC) and unilaterally hysterectomized-ovariecto- mized (UHOX) gilts was characterized between days 20 and 100 of gestation to evaluate the effects of intra-uterine crowding in UHOX gilts having essentially the same number of potential embryos, but only one-half the endometrial surface area of IC gilts. Results indicated that the number of live and dead embryos, percent fetal survival, fetal crown-rump length and fetal weight were not significantly (P>.10) different prior to day 35 of gestation in IC and UHOX gilts; however, all placental measurements were significantly (P~.01) greater in IC gilts at all stages of gestation. The data suggest that placental insufficiency was the primary cause of increased fetal death and decreased fetal growth which occurred after day 35 of gestation in UHOX gilts. Fetal growth was significantly (P
This paper presents characteristics of different polyclonal antisera raised against several steroid and protein antigens: 1/ primary antisera against steroid hormones: estradiol-17beta (anti-E2), estrone (anti-E1), testosterone (anti-T), androstendione (anti-A4), cortisol (anti-F) and corticosterone (anti-B); 2/ primary antisera against porcine luteinizing hormone (anti-pLH) and against different forms of porcine pregnancy associated glycoproteins (anti-pPAG) - proteins produced by chorionic tissue; 3/ secondary monovalent antisera raised against rabbit gamma-globulins (Sm-r); 4/ secondary polyvalent antisera against rabbit, pig and quinea pig gamma-globulins mixed at a ratio 1:1:1 (Sp-rpq). All antisera described in the paper present sufficient quality to be routinely used in various RIA, ELISA or Western determinations in physiological and clinical studies of reproductive processes. The antisera against steroid hormones and pLH are available on request.
Significant advances have taken place in our knowledge of the enzymes involved in steroid hormone biosynthesis since the last comprehensive review in 1988. Major developments include the cloning, identification, and characterization of multiple isoforms of 3beta-hydroxysteroid dehydrogenase, which play a critical role in the biosynthesis of all steroid hormones and 17beta-hydroxysteroid dehydrogenase where specific isoforms are essential for the final step in active steroid hormone biosynthesis. Advances have taken place in our understanding of the unique manner that determines tissue-specific expression of P450aromatase through the utilization of alternative promoters. In recent years, evidence has been obtained for the expression of steroidogenic enzymes in the nervous system and in cardiac tissue, indicating that these tissues may be involved in the biosynthesis of steroid hormones acting in an autocrine or paracrine manner. This review presents a detailed description of the enzymes involved in the biosynthesis of active steroid hormones, with emphasis on the human and mouse enzymes and their expression in gonads, adrenal glands, and placenta.
Inhibition of luteolysis and establishment of pregnancy in pigs results from oestrogen secretion by the conceptuses and requires progesterone produced by the corpus luteum (CL). An integral part of maternal recognition of pregnancy in the pig is the redirection of prostaglandin (PG) F2alpha secretion from endocrine (blood) to exocrine (uterus) direction and an increase of PGE2 synthesis in both the endometrium and conceptus. Uterine and conceptus PGE2 synthases play an integrated role in establishing the PGE2:PGF2alpha ratio necessary for luteal maintenance. The luteolytic or luteotrophic changes in the CL are synchronised with the release of maternal pituitary and ovarian hormones. The presence of uterine oxytocin (OT) and luteinising hormone (LH) receptors are important for the luteolytic effect of PGF2alpha. Conceptus oestrogen secretion coincides with autocrine and paracrine dialogue between the multiple conceptuses and uterine biological compounds and their receptors in trophoblast and endometrium.
In Europe household appliances are a major source of indoor 50 Hz magnetic field exposure. A number of epidemiological studies have reported associations between leukemia risk and personal use of household appliances. In the "Norddeutsche Leukämie und Lymphomstudie" (NLL), which was conducted in Northern Germany (Schleswig-Holstein and Lower Saxony) between 1997 and 2001, lifetime use of a preselected array of electric appliances (microwave ovens, hair-dryers, motorized electrical alarm clocks (i.e. that use a motor to move their hands or digits), electric blankets and pillows, heated waterbeds, computers with conventional screens, TVs, and electric sewing machines) was recorded in a standardized, personal, computerized interview. Exposure was assessed on three different levels of precision: ever use, cumulative appliance-years, and average time of daily use. Additional questions referred to exposure modifying factors, including distance from screen while watching TV, position of an alarm clock at the bed etc.). Exposure to ELF-EMF from household appliances was quantified as ever vs. never use, gross and net appliance-years of lifetime use and cumulative microT-hours. Flux densities were based on measurements of appliances from the published literature. These were used as weighting factors to account for the different device-specific contributions to overall ELF-EMF exposure. Resulting distributions (as quartiles) for exposure scores revealed systematic differences for different levels of precision. Our analysis indicates that valid assessment of ELF-EMF exposure from household appliances should be based on the highest possible degree of precision and hence provides a considerable challenge in analytic epidemiology.
The effects of extremely low-frequency (ELF) magnetic fields on sex hormones of adult female Spague-Dawley rats were investigated. Adult female rats were exposed to a 50 Hz sinusoidal magnetic field at approximately 25 microT (rms) for 18 weeks before they returned to their normal life with unexposed counterparts. Serum level of Luteinizing Hormone (LH), Follicle Stimulating Hormone (FSH), progesterone, and estrogen were measured before, after, and during the exposure. Body and uterine weights were not affected by the field. A significant reduction in absolute and relative ovarian weights in exposed rats was observed when compared with sham-exposed controls (P < 0.05). The reduction in the levels of gonadotropins (FSH and LH) was significant after six weeks of exposure (P < 0.005). FSH levels were affected only on week 6 of exposure while LH remained affected during at 12 and 18 weeks (P < 0.05). Interestingly, no significant effects were found at 6 and 12 weeks after removing the field. The level of progesterone and estrogen was significantly decreased after 12 weeks of exposure (P < 0.05), while no other effects on progesterone level was observed during exposure or after removing the exposure. The level of estrogen was also significantly reduced at 12 weeks after removing the field (P < 0.05). These results suggest possible adverse effect on mammalian fertility and reproduction. The effects of ELF-MF on sex hormones were shown to be partly reversible.
Past studies of the oviducts have documented oviductal steroid production during the oestrous cycle in pigs. The present study examined whether the pig oviducts are the source of steroid hormones during early pregnancy. In the ampulla and isthmus, the expression of 3β-hydroxysteroid dehydrogenase (3βHSD) and aromatase cytochrome P450 (CYP19) mRNA by real-time PCR, cellular localization and quantities of the studied proteins by immunofluorescence and Western blot analysis, and concentration of steroid hormones in oviductal flushings by radioimmunoassay, were studied. The expression of 3βHSD in the ampulla and isthmus was correlated (r = 0.89) and higher on Days 2-3 and 15-16 than on Days 10-11 and 12-13. CYP19 expression was elevated in the ampulla on Days 2-3, 10-11 and 15-16 and in the isthmus on Days 2-3 vs. the other days studied. The studied proteins were localized in oviductal epithelial cells. In the ampulla, the quantity of 3βHSD protein did not change, and was greater in the isthmus on Days 2-3 vs. Days 12-13 of pregnancy. The P450arom protein quantity increased in the ampulla on Days 2-3 vs. Days 10-11 and 15-16 and vs. Days 10-11 and 12-13 in the isthmus. The concentrations of progesterone and androstenedione in oviductal flushings were lowest on Days 12-13 and on Days 2-3 and 15-16, respectively, while oestradiol-17β and oestrone levels did not change. Porcine oviducts are the sources of steroid hormones during early pregnancy. The expression of steroidogenic enzymes primarily increases during the embryos presence in the oviduct, i.e., on Days 2-3 of pregnancy.
An electromagnetic field (EMF) of extremely low frequency may affect physiological processes in mammals. The aim of the present study was to determine the effect of an EMF on the synthesis and secretion of oestradiol-17β (E2) in the porcine uterus. Endometrial and myometrial slices were harvested on days 12-13 of the oestrous cycle and exposed in vitro to an EMF (50 and 120 Hz, 8 mT) for 2 and 4 h in the presence or absence of progesterone (P4). Subsequently, the incubation media were used to determine the concentration of E2 with RIA. Tissues fragments were used to study the expression of CYP19A3 mRNA using Real-Time PCR and the abundance of P450 aromatase using Western Blotting. The 50-Hz EMF increased E2 release from the endometrium and the myometrium at both time points of in vitro incubation. A 120-Hz EMF decreased the endometrial secretion of E2 after 2 h of incubation and did not affect E2 secretion after 4 h. In the myometrium, the 120-Hz EMF increased E2 secretion after 4 h of incubation. In P4-treated uterine fragments, no significant EMF exposition-related changes were observed. Only myometrial fragments incubated in the presence of P4 at 120-Hz EMF (4 h) released higher amounts of E2 due to EMF treatment. The 50-Hz EMF exposure did not change the CYP19A3 mRNA expression in endometrial fragments incubated in the presence or absence of P4. In myometrial fragments, the highest CYP19A3 mRNA expression was observed in fragments not exposed to the 50-Hz EMF and P4-treated tissues compared to that in fragments exposed to 50 Hz EMF and incubated with or without P4 and control (no EMF and no P4) fragments. The EMF at 120 Hz decreased basal endometrial CYP19A3 mRNA expression and did not change the expression in the P4-treated endometrium. In the myometrium, the EMF at 120 Hz increased CYP19A3 mRNA expression in slices incubated without P4 and had no effect in the presence of P4. The EMF exposure (50 and 120 Hz) did not affect P450 aromatase abundance in either the endometrium or the myometrium. In conclusion, the EMF induces changes in the synthesis and release of E2 in uterine tissues harvested during days 12-13 of the oestrous cycle. These changes are related to the EMF frequency used, the time of the exposition and the presence of P4. We suspect that this observed phenomenon might lead to changes in the intrauterine milieu of oestrogen, which is crucial for the proper activity of uterine tissues during the mid-luteal phase of the oestrous cycle.
Purpose: The purpose of this study was to use histological and biochemical methods in order to evaluate changes taking place in the ovaria of rats exposed to the effect of a 900-Megahertz (MHz) electromagnetic field (EMF) in middle and late adolescence.
Materials and Methods: Twenty-four 34-day-old female Sprague Dawley rats were assigned equally into control, sham and EMF groups. EMF group rats were exposed to the effect of a 900-MHz EMF for 1 hour a day, at the same time every day between postnatal days 35 and 59, while inside an EMF cage. Sham group rats were kept inside the EMF cage for the same time between postnatal days 35 and 59 without being exposed to any EMF effect. At the end of the study, rats’ ovaria were removed and blood specimens were taken. Right ovarium tissues were subjected to routine histological procedures and stained with hematoxylin and eosin, periodic acid shift and Masson’s trichrome. Follicles were counted in ovarian sections stained with hematoxylin and eosin. The TUNEL method was used to evaluate apoptosis. Left ovarian tissue and blood specimens were investigated biochemically.
Results: Histopathological examination of EMF group ovarian tissue revealed thinning in the zona granulosa and theca layers, shrinking in granulose cells, reduced mitotic activity and leukocyte infiltration in the follicles and stroma. Secondary follicle numbers in the EMF group were significantly lower than in the other groups. In terms of biochemistry, EMF and sham group superoxide dismutase, catalase and anti-Mullerian hormone levels and EMF group 3-nitrotirosin values increased significantly compared to the control group. EMF and sham group serum catalase and 8-hydroxy-deoxiguanosine values increased significantly compared to the control group, and EMF group total oxidant status and oxidative stress index values were significantly higher compared to the sham and control groups.
Conclusions: 900-MHz EMF applied in middle and late adolescence may cause changes in the morphology and biochemistry of the rat ovarium.
The impact of electromagnetic fields (EMF) on the pineal gland has been described in numerous studies, but many questions still remain unanswered. The aim of the experiment described in this study was to evaluate the effect of EMF on the viability of the pineal gland cells of pig in vitro. Primary culture of the pineal gland cells has been exposed to the influence of an EMF at a frequency of 50 Hz with 1, 2 or 3 hours and for 3 hours every 2 or 3 days. After the experiment, viability of cells was assessed by MTT assay and compared to a control culture not exposed to electromagnetic fields. We noticed that in respect to the control, exposure of the cells to the EMF induced a significant increase in viability of cells at 2 and 3 hours of exposure. After three days of 3-hour exposure to EMF, we observed a significant decrease in cell viability in relation to the control. The results of these studies suggest that EMF can have a significant biological effect on the cells of the pineal gland in a time-dependent exposure to its action.
Studies have suggested that exposure to extremely low frequency electromagnetic fields (ELF-EMF) may be associated with increased risk of adverse birth outcomes. This study tested the hypothesis that close proximity to residential ELF-EMF sources is associated with a reduction in birth weight and increased the risk of low birthweight (LBW), small for gestational age (SGA) and spontaneous preterm birth (SPTB). Closest residential proximity to high voltage cables, overhead power lines, substations or towers during pregnancy was calculated for 140356 singleton live births between 2004 and 2008 in Northwest England. Associations between proximity and risk for LBW, SGA and SPTB were calculated, as well as associations with birth weight directly. Associations were adjusted for maternal age, ethnicity, parity and for part of the population additionally for maternal smoking during pregnancy. Reduced average birth weight of 212 g (95% confidence interval (CI): -395 to -29 g) was found for close proximity to a source, and was largest for female births (-251 g (95% CI: -487 to -15 g)). No statistically significant increased risks for any clinical birth outcomes with residential proximity of 50 m or less were observed. Living close (50 m or less) to a residential ELF-EMF source during pregnancy is associated with suboptimal growth in utero, with stronger effects in female than in males. However, only a few pregnant women live this close to high voltage cables, overhead power lines, substations or towers, likely limiting its public health impact. Bioelectromagnetics. © 2014 Wiley Periodicals, Inc.
A major limitation for increasing litter size in swine is embryonic loss that occurs during the 2nd to 3rd wk of gestation. High ovulation rates of modern sows have more than supplied the potential number of embryos necessary to improve litter size. The current challenge is determining how early conceptus development affects the ability to maintain the viability through the remaining 90 d of gestation to maximize farrowing house production. To achieve this, it is neces- sary to identify and understand the possible causes of embryonic death. Because fertilization rates are gener- ally high in swine, early embryonic loss during the first 20 d of gestation is considered to critically effect poten- tial litter size. There are three periods during which early embryonic loss can occur: 1) pre-elongation devel- opment, 2) trophoblastic elongation, and 3) placental attachment. The first two periods are related to time of fertilization and subsequent developmental rate for each individual embryo within the litter. Asynchrony in embryonic development relative to uterine develop-
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The increasing focus on the pig as a biomedical model calls for studies which investigate morphological and molecular mechanisms during initial embryonic development in this species. In the pig, the paternal genome is actively demethylated in the zygote, whereas the maternal genome remains methylated. The major genome activation occurs at the four‐cell stage, when prominent ribosome‐synthesizing nucleoli develop in the blastomeres, allowing for trophectoderm and inner cell mass (ICM) differentiation. Unlike in mice, the pluripotency gene OCT4 is initially expressed in both compartments. The ICM differentiates into epiblast and hypoblast approximately at the time of hatching from the zona pellucida, and subsequently the loss of the Rauber’s layer results in an uncovered epiblast establishing the embryonic disc again in contrast to mice. This particular and protracted ICM/epiblast biology may contribute to the lack of success in culturing porcine embryonic stem cells. The embryonic disc subsequently becomes polarized by a posterior thickening, which includes ingression of the first extra‐embryonic mesoderm. Thereafter, the primitive streak forms and gastrulation results in formation of the somatic germ layers and germline, i.e. the primordial germ cells. The latter remain pluripotent for a period and may be isolated and cultured as embryonic germ cells in vitro .
Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones. Whereas most endocrine texts discuss adrenal, ovarian, testicular, placental, and other steroidogenic processes in a gland-specific fashion, steroidogenesis is better understood as a single process that is repeated in each gland with cell-type-specific variations on a single theme. Thus, understanding steroidogenesis is rooted in an understanding of the biochemistry of the various steroidogenic enzymes and cofactors and the genes that encode them. The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by a single enzyme, P450scc (CYP11A1), but this enzymatically complex step is subject to multiple regulatory mechanisms, yielding finely tuned quantitative regulation. Qualitative regulation determining the type of steroid to be produced is mediated by many enzymes and cofactors. Steroidogenic enzymes fall into two groups: cytochrome P450 enzymes and hydroxysteroid dehydrogenases. A cytochrome P450 may be either type 1 (in mitochondria) or type 2 (in endoplasmic reticulum), and a hydroxysteroid dehydrogenase may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families. The activities of these enzymes are modulated by posttranslational modifications and by cofactors, especially electron-donating redox partners. The elucidation of the precise roles of these various enzymes and cofactors has been greatly facilitated by identifying the genetic bases of rare disorders of steroidogenesis. Some enzymes not principally involved in steroidogenesis may also catalyze extraglandular steroidogenesis, modulating the phenotype expected to result from some mutations. Understanding steroidogenesis is of fundamental importance to understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiological homeostasis.
Modern society continuously exposes the population to electromagnetic radiation, the effects of which on human health, in particular reproduction, are still unknown. The aim of this research was to assess the effect of acute (1h) exposure of boar spermatozoa to a 50 Hz extremely low frequency electromagnetic field (ELF-EMF) on early fertility outcome. The effect of intensities ranging from 0 to 2 mT on morpho-functional integrity of capacitated spermatozoa was examined in vitro. The oviducts containing or without spermatozoa were then exposed to the minimum in vivo, TD(50,) and maximum intensities determined in vitro, 4h before ovulation. The effects of ELF-EMF on spermatozoa in terms of early embryo development were evaluated after 12h and 6 days. It was found that in vitro ELF-EMF > 0.5 mT induced a progressive acrosome damage, thus compromising the ability of spermatozoa to undergo acrosomal reaction after zona pellucida stimulation and reducing the in vitro fertilization outcome. These effects became evident at 0.75 mT and reached the plateau at 1 mT. Under in vivo conditions, the ELF-EMF intensity of 1 mT was able to compromise sperm function, significantly reducing the fertilization rate. In addition, the exposure of oviducts to fields > or = 0.75 mT in the absence of spermatozoa was able to negatively affect early embryo development. In fact, it was found to cause a slowdown in the embryo cleavage. In conclusion, it was demonstrated how and at which intensities ELF-EMF negatively affect early fertility outcome in a highly predictive animal model.
Porcine (Sus scrofa domestica) uterine slices harvested during both early pregnancy and luteolysis produce steroid hormones. The aim of the present study was to determine (1) which porcine separated uterine cells secrete androgens: androstenedione (A(4)) and testosterone (T), and estradiol-17beta (E(2)) in culture; (2) if the production of A(4), T and E(2) in the uterine cells is regulated by P4 and OT; (3) if uterine tissues expressed cytochrome P450arom gene (CYP19). Uteri were collected on Days 14 to 16 of early pregnancy and the estrous cycle. Enzymatically separated epithelial cells, stromal cells, and myocytes were cultured in vitro for 2, 6, and 12h with control medium, progesterone (P(4); 10(-5) M), oxytocin (OT; 10(-7) M), and both hormones (P(4)+OT). The studied cells secreted A(4), T, and E(2) in vitro. Progesterone served as a substrate for steroid synthesis in the uterine cells. Isolated uterine cells, cultured separately, contributed in equal portion to the basal production of androgens (A(4) and T) during both early pregnancy and luteolysis. In pregnant pigs, the epithelial and stromal cells were rich sources of E(2) compared with myocytes. Myocytes produced E(2) mainly during luteolysis. Pregnant porcine endometrium and myometrium expressed the gene CYP19, which encodes for P450 aromatase, a steroidogenic enzyme. The results indicate an active steroidogenic pathway in porcine uterine cells. The epithelial cells, stromal cells, and myocytes participate in steroid production as an alternative source for their action in pigs.
Currently, a lack of consensus exists on how best to perform and interpret quantitative real-time PCR (qPCR) experiments. The problem is exacerbated by a lack of sufficient experimental detail in many publications, which impedes a reader's ability to evaluate critically the quality of the results presented or to repeat the experiments.
The Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines target the reliability of results to help ensure the integrity of the scientific literature, promote consistency between laboratories, and increase experimental transparency. MIQE is a set of guidelines that describe the minimum information necessary for evaluating qPCR experiments. Included is a checklist to accompany the initial submission of a manuscript to the publisher. By providing all relevant experimental conditions and assay characteristics, reviewers can assess the validity of the protocols used. Full disclosure of all reagents, sequences, and analysis methods is necessary to enable other investigators to reproduce results. MIQE details should be published either in abbreviated form or as an online supplement.
Following these guidelines will encourage better experimental practice, allowing more reliable and unequivocal interpretation of qPCR results.
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Previously, we found that in addition to embryos, the uterine tissues may be a source of estradiol-17beta (E(2)) during early pregnancy in the pig. The aim of the present study was to determine whether porcine endometrium and myometrium secrete androgens - androstenedione (A(4)), testosterone (T) and estrone (E(1)) during early pregnancy and luteolysis (Days 14-16) in pigs. Individual endometrial and myometrial slices (200 mg) were first pre-incubated (24 h) and then incubated (6 h, 37 degrees C in an atmosphere of 95% O(2) and 5% CO(2)) in the presence or absence of progesterone (P(4); 10(-5) M), oxytocin (OT; 10(-7) M) or OT plus P(4). Basal endometrial and myometrial secretion of A(4) and T did not differ between pregnant and cyclic gilts. Endometrial secretion of E(1) was higher in pregnant than cyclic gilts (p<0.05) while myometrial secretion of E(1) did not differ between the two groups of the examined pigs (p>0.05). Progesterone significantly increased A(4) and T secretion (p<0.001) by uterine tissues regardless of the reproductive status. In the presence of P(4), endometrial and myometrial secretion of E(1) was increased only during luteolysis (p<0.001). In both tissues, OT did not affect the examined steroid secretion and did not change the effect of P(4).
In conclusion:
1) porcine endometrium and myometrium was found to produce A(4), T and E(1) in vitro; 2) basal endometrial and myometrial production of A(4) and T did not differ between the examined reproductive periods; 3) the endometrium released more E(1) during early pregnancy than luteolysis; 4) in the presence of substrate (P(4)), uterine tissues increased secretion of A(4) and T during early pregnancy and luteolysis; and 5) P(4) increased uterine production of E(1) only during luteolysis. These data demonstrated the presence of the active steroid pathway in porcine endometrium and myometrium which may serve as an alternative source of androgens and estrogens in pigs.
To elucidate the morphology of the initial stages of epitheliochorial placentation in the pig, material from 10 sows of the Danish Landrace and from one Göttinger minipig gilt from day 13 to day 26 of gestation was processed for scanning and transmission electron microscopy. The observed foetomaternal interaction from day 19 1/2 minipig placenta corresponded well to the observations on the Danish Landrace placenta. From the results and the discussion it was concluded that the following structures were implicated in the initial phases of placentation in the pig: Protruding epithelial proliferations of the uterine epithelium enclosed by chorionic caps serving to immobilize the blastocyst (days 13 and 14). A thick glycocalyx on the maternal and a thin one on the foetal epithelium before contact. Close apposition between the apical plasma membranes from trophoblastic and uterine epithelium (day 14). Development of interdigitating microvilli (days 15-16). Formation of apical domes on the uterine epithelium closely related to the trophoblast provided with long cytoplasmic extensions into a luminal space between the apical domes, apparently representing a transition from histiotropic to haemotrophic nutrition (days 15-20). Placentation, development of interdigitating microvilli between foetal and maternal epithelium, was extended but not terminated in the peripheral zone at day 26.
Pregnancy recognition in pigs occurs between Days 11 and 12 when blastocysts undergo transformation from the spherical to filainentous form. This study evaluated the relationship between blastocyst development and total calcium (Ca), estrone (E, ), estradiol (E2), estriol (E3), E1 sulfate (E1S), E2S, E3S, prostaglandin F (PGF), PGE2, protein (Pr) and acid phosphatase (AP) activity in uterine flushings obtained from pregnant gilts between Days 10 and 14. Data from pregnant gilts were compared to those obtained from uterine flushings collected between Days 10 and 14 of the estrous cycle. Surface and ultrastructural changes in the endometrium associated with blastocyst development were evaluated by scanning (SEM) and transmission (TEM) electron microscopy. Pregnant uterine flushings were analyzed relative to average size of blastocysts recovered: 5 mm spherical, 5-8 mm spherical, 9-50 mm tubular, and >50 mm filamentous Day 12 and Day 14. Nonpregnant gilt uterine flushings were analyzed by Day of the estrous cycle (10.5, 11, 11.5, 12 and 14). Total E2 content increased almost 4-fold in pregnant uterine flushings containing tubular blastocysts (2.3 ng) as compared with flushings with spherical blastocysts (0.6 ng) and continued to increase as the blastocysts became filamentous (4.4 ng) but had declined by Day 14 (0.4 ng). The pattern of change for total recoverable E, and E3 was similar to that for E2 and the highest values were obtained in uterine flushings with filamentous blastocysts. A concomitant increase in E, S and E2 S content also was detected in flushings with tubular and Day 12 filamentous blastocysts. Total Ca, Pr, AP, PGF, and PGE2 content increased in association with increased E2 in flushings. The increase in Pr, AP, PGF and PGE2 content in pregnant flushings continued to Day 14. However, Ca content had declined by Day 14 (0.1 mg) after a transient increase to 1.5 mg in flushings that contained tubular blastocysts (Days 11 and 12). Comparable changes in estrogens, proteins, Ca, PGF and PGE2 content in nonpregnant uterine flushings collected between Days 10.5 and 14 were not detected. Electrophoresis of protein in pregnant uterine flushings indicated that the appearance of three basic uterine proteins (Mr 32K to 60K) were associated with the increase in estrogen. These proteins were detected in flushings with tubular and filamentous blastocysts (Day 12), but were not found until Day 14 in nonpregnant gilts. A synchronized release of secretory vesicles from the glandular epithelium was observed by TEM which indicated a close association between formation of tubular blastocysts, onset of blastocyst estrogen production and increased protein in uterine flushings. Although secretion was detected in nonpregnant glandular epithelium, no synchronized release was observed. Results suggest that estrogen production by tubular and early filamentous blastocysts (Day 11.5-12.0) stimulates secretion of protein from the endometrium which may be mediated through an effect of free Ca on the uterine glandular epithelium. Increases in PGF and PGE2 were associated closely with estrogen production and blastocyst elongation.
The formation of estrogens in mammals via aromatase involves the relatively unique capacity to form an aromatic ring de novo in contrast to most other aromatic substances (essential amino acids) which are obtained only in the diet. The reaction is the only example of a cytochrome P450 system which resides in both the mitochondrial and microsomal fractions of the cell. It occurs widely throughout the body in diverse tissues and functions via both de novo synthesis and transformation of prehormones (androstenedione and testosterone). It is found widely in animal species in both the brain and gonads even in phylogenetically primitive species. Placental aromatase appears to be associated with the evolution of viviparity and an extended gestational period in utero. Follicular aromatase which is dependent upon follicle-stimulating hormone stimulation appears to be essential for oogenesis, ovulation, and normal luteal functions while central nervous system aromatase serves to determine sexual behavior and the neurohormonal link to the hypothalamus and pituitary for ovarian cyclicity. While estrogens are the key to pituitary, breast, and endometrial growth and development, this hormone is one of the few examples of an endogenous steroid that has been implicated as a carcinogen or a stimulant for carcinogenesis.
It has been hypothesized that conceptus estrogens influence endometrial protein secretion during pregnancy in swine. To test this hypothesis, the effect of estrone and estradiol treatment from d 30 to 60 of pregnancy or pseudopregnancy on endometrial protein secretion was investigated. Pregnant (P; n = 16) and pseudopregnant (PP) gilts (n = 18) received either sham treatment or estrone or estradiol implants (5 mg/d release rate; 60 d release) on d 30 of P or PP. Blood samples were collected on d 30, 40, 50, and 60 to measure estrone and estradiol. On d 60, gilts were hysterectomized. For P gilts, endometrium in apposition to one placenta from each uterine horn was collected. For PP gilts, each uterine horn was flushed with 40 mL of leucine-deficient minimal essential medium (MEM), and endometrial tissue was collected from each horn. Endometrial tissues were incubated in MEM in the presence of 50 microCi of [3H]leucine to examine protein secretion. Estrone and estradiol treatments increased both plasma and endometrial concentrations of estrone (P < .01 except endometrium for P gilts) and estradiol (P < .01, respectively). Endometrium from P gilts secreted more nondialyzable macromolecules (NDM), acid phosphatase activity (AP, a measure of uteroferrin), and retinol-binding protein (RBP) in culture than did endometrium from PP gilts. Estrone treatment increased (P < .01) endometrial NDM from P gilts but not that from PP gilts; estradiol had no effect. Both estrone and estradiol increased (P = .069) endometrial secretion of AP of PP but not of P gilts. Endometrial secretion of RBP was not affected by either estrone or estradiol treatment. Neither estrone nor estradiol affected total protein or AP and estrone treatment decreased (P < .05) RBP in uterine flushings from PP gilts. These data indicate that endometrium from P pigs secretes more protein than endometrium from PP pigs but neither estrone nor estradiol completely mimics the effect of pregnancy.
While the ovaries are the principal source of systemic estrogen in the premenopausal nonpregnant woman, other sites of estrogen biosynthesis are present throughout the body and these become the major sources of estrogen beyond menopause. These extragonadal sources of estrogen are small, but may play an important, though hitherto largely unrecognized, physiological and pathophysiological role. Aromatase activity in extragonadal sites contributes to this source of estrogen and may contribute to breast tumor development and/or growth. Selective aromatase modulators (SAMs) may have a role to play in the treatment of estrogen-dependent diseases, such as breast cancer.
Groups of mated female Sprague-Dawley rats were simultaneously exposed to 0 (sham exposed), 7, 70, or 350 microT (rms) circularly polarized 50 Hz magnetic fields (MF) for 22 h/day on gestational day 8-15, the period of rat fetal organogenesis (organogenesis study) or from day 0 to day 7 of gestation, the rat preimplantation period (preimplantation study). Developmental toxicity was assessed on gestational day 20. Identical experiments were repeated to confirm reproducibility of both studies. In both studies, statistically significant differences between exposed and sham exposed animals were observed in several measured parameters; however, these differences only appeared in one, but not both replicate experiments and generally at only an isolated exposure level. Because these differences were not reproducible and did not show a dose response relationship, they were not considered related to MF exposure. In the organogenesis study, lower kidney weights of dams were seen at 70 and 350 microT in Experiment 1. Lower dam liver weights and lower mean body weights of viable female and male fetuses were seen at 70 microT in Experiment 2. Otherwise, there were no differences in these parameters or in group means for fetal loss after implantation, number of viable fetuses, fetal body weight and sex ratio, incidences of external, visceral, and skeletal abnormalities or variations, or tissue abnormalities after histopathological examination. In the preimplantation study, dam health and indices for reproduction and embryo-fetal development, including pre or postimplantation loss, number and body weight of live fetuses, and sex ratio, external, skeletal abnormalities and variations, and skeletal ossification did not differ. Dam inorganic phosphorous concentration at 350 microT was elevated in one experiment and depressed in another. In one experiment, visceral abnormalities, primarily thymic remnant in neck and accessory liver lobe, were increased in the 7 microT group. Based on these results from two studies, we conclude that circularly polarized 50 Hz MF exposure of up to 350 microT during the fetal organogenesis or during the preimplantation period does not affect reproduction and embryo-fetal development in Sprague-Dawley rats.
In 1977 Bazer and Thatcher proposed that maternal recognition of pregnancy in the pig involves the secretion of PGF(2alpha) towards the uterine lumen (exocrine) rather than towards the uterine venous drainage (endocrine) as occurs in the non-pregnant pig during the mid to late stages of the estrous cycle. The retrograde transfer of PGF(2alpha) from the venous blood and uterine lymph into the uterus and the ability of the uterine vein and artery wall to accumulate PGF(2alpha) could constitute a part of putative mechanism of corpus luteum protection during early pregnancy. A luteotropic/anti-luteolytic effect of PGE(2) in the pig also has been frequently demonstrated and it seems that the most effective agent in changing PGE(2):PGF(2alpha) secretion is estradiol. The role for oxytocin during luteolysis and early pregnancy is controversial. It appears, however, that the main function of this hormone is autocrine and/or paracrine stimulation of PGF(2alpha) secretion. Pig trophoblastic interferons, unlike those of ruminants, do not themselves exert an anti-luteolytic effect in pigs. It is likely, that cytokines and angiogenic growth factors are involved in the initiation of luteolysis and/or maintenance of corpora lutea (CL).A discovery of functional LH receptors in porcine endometrium opened a new possibility for this hormone in luteolysis and perhaps in recognition of pregnancy in pigs. The endogenous LH pulses can provoke prostaglandin secretion from endometrium in pigs. On the other hand prolongation of up-regulation of LH receptors in endometrium of early pregnant gilts can additionally increase angiogenic factor production before the process of implantation is completed. Finally new integrated concepts of luteolysis and inhibition of luteolysis in pigs based on selectively reviewed information are presented.
Progesterone is unequivocally required for maternal support of conceptus (embryo/fetus and associated extraembryonic membranes) survival and development. In cyclic sheep, progesterone is paradoxically involved in suppressing and then initiating development of the endometrial luteolytic mechanism. In cyclic and pregnant sheep, progesterone negatively autoregulates progesterone receptor (PR) gene expression in the endometrial luminal (LE) and superficial glandular epithelium (GE). In cyclic sheep, PR loss is closely followed by increases in epithelial estrogen receptor (ERalpha) and then oxytocin receptor (OTR), allowing oxytocin to induce uterine release of luteolytic prostaglandin F2alpha pulses. In pregnant sheep, the conceptus produces interferon tau (IFNtau) that acts on the endometrium to inhibit transcription of the ERalpha gene and thus development of the endometrial luteolytic mechanism. After Day 13 of pregnancy, the endometrial epithelia do not express the PR, whereas the stroma and myometrium remain PR positive. The absence of PR in the endometrial GE is required for onset of differentiated function of the glands during pregnancy. The sequential, overlapping actions of progesterone, IFNtau, placental lactogen (PL), and growth hormone (GH) comprise a hormonal servomechanism that regulates endometrial gland morphogenesis and terminal differentiated function during gestation. In pigs, estrogen, the pregnancy-recognition signal, increases fibroblast growth factor 7 (FGF-7) expression in the endometrial LE that, in turn, stimulates proliferation and differentiated functions of the trophectoderm, which expresses the receptor for FGF-7. Strategic manipulation of these physiological mechanisms may offer therapeutic schemes to improve uterine capacity, conceptus survival, and reproductive health of domestic animals and humans.
The objective of this study was to monitor and compare follicle populations and follicular development in pregnant and nonpregnant sows from Day 3 to Day 20 after breeding. Twenty-four sows were paired within parity on the day of artificial insemination and were randomly allocated within pair for insemination with either killed (n=12) or live spermatozoa (n=12). All the sows were artificially inseminated with the pooled ejaculate of the same boar. From Day 3 through Day 20 post estrus, ovarian follicles were scanned daily by ultrasonography. Ultrasound images were recorded on videotape and were retrospectively analyzed. Follicles were mapped to identify the existence of follicular waves. The follicles were then classified as small (< 3 mm), medium (3-5 mm), or large (> or =5 mm). Pregnancy diagnosis was performed on Day 21 by ultrasonography. Pregnant sows maintained a constant proportion of the follicle population in the small, medium and large follicle categories. However, in the nonpregnant sows, the proportion of follicles in the various size categories remained constant until Day 15. Thereafter, the proportion of small follicles decreased (P < 0.05) from Day 15 to 20, and the proportions of medium and large follicles increased (P < 0.05). The predictability of pregnancy status on Day 20 based on follicle populations in any of the 3 follicle categories was low. Moreover, there was no evidence of follicular waves during the estrous cycle or early pregnancy. In conclusion, the proportion of small follicles decreased while medium and large follicle increased from Day 15 through Day 20 of the estrous cycle, but not during a similar stage of pregnancy. This latter finding concurs with follicle recruitment from the pool of small follicles for ovulation following PGF2alpha secretion to induce luteolysis, which reduces progesterone concentrations and thereby allows for the stimulation of the pool of small follicles by gonadotropins.
Past studies of the source of estrogens secreted during maternal recognition of pregnancy in pigs have focused on embryonic rather than uterine origin of these steroids. The present study documents: (1) the expression of the gene CYP 17, encoding cytochrome P450 17alpha-hydroxylase/C(17-20) lyase and (2) the synthesis and secretion of estradiol-17 beta (E(2)) in endometrial and myometrial tissues in gilts. The expression of CYP 17 gene was shown in porcine endometrium and myometrium. Basal endometrial secretion of E(2) was higher in pregnant gilts than in cyclic gilts (days 14-16). The myometrium secreted more E(2) during the expected time of luteolysis compared to early pregnancy. Basal secretion of E(2) during pregnancy was higher from the endometrium than from the myometrium. Conversely, during luteolysis E(2) secretion was higher from the myometrium and lower from the endometrium. In pregnant and cyclic gilts (days 14-16), progesterone (P(4), 10(-5)M) in vitro significantly increased E(2) secretion regardless of reproductive status. Oxytocin (OT, 10(-7)M) had no influence on E(2) secretion and did not change the stimulatory effect of P(4) in both tissues examined. In conclusions: (1) the CYP 17 gene transcript is present in porcine endometrium and myometrium; (2) porcine endometrium and myometrium release E(2) in vitro; (3) the endometrium releases more E(2) than the myometrium during early pregnancy; (4) the myometrium releases E(2) mainly during luteolysis; (5) the endometrium and myometrium can increase E(2) release in vitro if substrate (P(4)) is provided during early pregnancy and luteolysis. These data suggest active estrogen production by the myometrium and endometrium as an alternative source for this signal for recognition of pregnancy in the pig.
Radioimmunoassay of steroid hormones in biological fluids
- Ciereszko