Horacio Croxatto

• Andrés Bello University

During mating, males provide not only the spermatozoa to fertilize the oocyte but also other stimuli that are essential for initiating and maintaining the reproductive programme in females. In the mammalian oviduct, mating regulates sperm storage, egg transport, fertilization, early embryonic development, and oestradiol metabolism. However, the mai...

Progesterone regulates uterine function during the luteal phase and is essential for the acquisition of endometrial receptivity. The objective of the present study was to identify endometrial transcripts whose expression is altered during the window of implantation after the administration of 200mg of the antiprogestin mifepristone, 48 hours after...

Objective To determine whether a 3-month contraceptive vaginal ring (CVR) delivering ulipristal acetate (UPA) can inhibit ovulation in 90% of cycles. Study Design This was a randomized dose-finding parallel group clinical trial. Fifty-five healthy women with normal ovulation at baseline were randomized to receive a low-dose (1500 μg/day) or a high...

Background Endometrial function is essential for embryo implantation. The aim of this study was to analyze gene expression profiles from individual endometrial samples obtained from women with repeated implantation failure after IVF in oocyte donation programs. Methods Seventeen volunteers were recruited: women who had previously participated as r...

The days just prior to ovulation are the most crucial for emergency contraception (EC) efficacy. Ulipristal acetate (UPA) and levonorgestrel's (LNG) capacity to inhibit follicular rupture have never been compared directly at this time of the cycle. Raw data from three pharmacodynamics studies with similar methodology were pooled to allow direct com...

Reproductive success stems from a finely regulated balance between follicular maturation and atresia, in which the role of carbohydrate structure is poorly understood. Herein, we describe for the first time a fraction of purified recombinant human Follicle Stimulating Hormone (FSH) that is capable of bringing about the cell death of granulosa cells...

Objective: To determine the role of endothelin (EDN) signaling in the estradiol (E2) nongenomic and genomic mechanism that regulates egg transport in the oviduct. Methods: The effect of the selective agonists of ETA (BQ610) or ETB (BQ788) on the E2-induced egg transport acceleration in unmated and mated rats was compared. Then, the level and distri...

The mechanism of action of levonorgestrel (LNG) as emergency contraception (EC) remains a subject of debate and its effect on sperm function has been only partially explained. The aim of this study was to assess whether LNG at a similar dose to those found in serum following oral intake for EC could affect spermatozoa when exposed to human fallopia...

Progesterone receptor modulators (PRMs) delivered by contraceptive vaginal rings provide an opportunity for development of an estrogen-free contraceptive that does not require daily oral intake of steroids. The objective of this proof-of-concept study was to determine whether continuous delivery of 600-800 mcg of ulipristal acetate (UPA) from a con...

The hypothesis that levonorgestrel (LNG) used as an emergency contraceptive interferes with endometrial receptivity remains unproven. We compared the endometrial gene expression profile during the receptive period after administering a single dose of LNG 1.5 mg or placebo on day 1 of the luteal phase. An endometrial biopsy was done on day LH+7 or L...

The contraceptive efficacy of emergency contraceptive pills containing levonorgestrel (LNG-EC) has been estimated in most previous studies by judging the day of ovulation from presumptive menstrual cycle data, thus providing poorly reliable estimates. In the present study, the efficacy of LNG-EC was determined in 393 cycles by dating ovulation on t...

Mating changes the mechanism by which E2 regulates oviductal egg transport, from a non-genomic to a genomic mode. Previously, we found that E2 increased the expression of several genes in the oviduct of mated rats, but not in unmated rats. Among the transcripts that increased its level by E2 only in mated rats was the one coding for an s100 calcium...

The endometrium is a dynamic tissue whose changes are driven by the ovarian steroidal hormones. Its main function is to provide an adequate substrate for embryo implantation. Using microarray technology, several reports have provided the gene expression patterns of human endometrial tissue during the window of implantation. However it is required t...

Males are expected to assist their mates whenever this behaviour raises survival of offspring with little expense in terms of mating opportunities. At a more proximate level, cortisol and testosterone hormones seem involved in the expression of parental care in mammals. We examined the consequences to postnatal offspring development and survival of...

The type of estrogen and progestin as well as their doses, route and regimens of administration may each affect the benefit-risk profile of postmenopausal hormone therapy. The aim of this study was to evaluate the endometrial effect of progesterone released continuously from a vaginal ring, combined with transdermal estradiol in postmenopausal wome...

Current methods of hormonal emergency contraception (EC) are ineffective in preventing follicular rupture when administered in the advanced pre-ovulatory phase. This study was designed to determine the capacity of ulipristal acetate (UPA), a selective progesterone receptor modulator developed for EC, to block follicular rupture when administered wi...

We aimed to evaluate whether emergency contraception with levonorgestrel (LNG-EC) administered after ovulation is equally effective to LNG-EC administered before ovulation. We studied a cohort of women attending a family planning clinic for EC. From interview, we recorded menstrual history, time of intercourse and of intake of LNG-EC. On the day of...

Estradiol (E(2)) accelerates oviductal egg transport through intraoviductal non-genomic pathways in unmated rats and through genomic pathways in mated rats. This shift in pathways has been designated as intracellular path shifting (IPS), and represents a novel and hitherto unrecognized effect of mating on the female reproductive tract. We had repor...

There is evidence that cyclooxygenase-2 (COX-2) inhibitors can prevent or delay follicular rupture. COX-2 inhibitors, such as meloxicam, may offer advantages over emergency contraception with levonorgestrel, such as extending the therapeutic window for up to 24 h. We assessed the effect of meloxicam administered in the late follicular phase upon ov...

Mating changes the mode of action of 17beta-estradiol (E2) to accelerate oviductal egg transport from a nongenomic to a genomic mode, although in both pathways estrogen receptors (ER) are required. This change was designated as intracellular path shifting (IPS). Herein, we examined the subcellular distribution of ESR1 and ESR2 (formerly known as ER...

The acceleration of egg transport by estradiol in cyclic rats is dependent on its conversion to 2-methoxyestradiol and protein phosphorylation (non-genomic pathway), whereas in pregnant rats it is dependent on gene transcription (genomic pathway). Mating during 30 min is sufficient to silence this non-genomic pathway, but not to induce the genomic...

In the rat, administration of 2-metoxyestardiol (2ME) accelerates oviductal egg transport in cyclic but not in pregnant rats. This paradoxical effect is consequence of the silencing of a nongenomic pathway of E2 induced by mating in the oviduct. Since mating induces an inflammatory response in the female genital tract we propose that some cytokines...

The aim of the present study was to determine the endocrine activity of cultured early antral follicles (EAF) isolated from prepubertal diethylstilbestrol-treated rats. The effect of steroidogenic substrates and FSH on steroid, inhibin A and B, Pro-alphaC and activin A production was evaluated. Androsterone was the predominant steroid produced by E...

The Population Council studied a pre-coital contraceptive microbicide vaginal product containing levonorgestrel (LNG) as active component and Carraguard gel as a vehicle (Carra/LNG gel) for couples who engage in occasional unplanned intercourse. The objective of this study was to evaluate the effect of sexual intercourse after vaginal application o...

Gene expression profiling of normal receptive endometrium has been characterized, but intrinsic defects in endometrial gene expression associated with implantation failure have not been reported. Women who had previously participated as recipients in oocyte donation cycles and repeatedly exhibited implantation failure (Group A, study group) or had...

Estradiol (E(2)) accelerates oviductal egg transport through intraoviductal nongenomic pathways in cyclic rats and through genomic pathways in pregnant rats. This shift in pathways, which we have provisionally designated as intracellular path shifting (IPS), is caused by mating-associated signals and represents a novel and hitherto unrecognized phe...

The aim of this study was to examine the requirement of luteal progesterone or luteal estrogen for the establishment of pregnancy in the Cebus monkey and to test in a primate species the synergism between RU 486 and letrozole (LTZ) found in rodents for inhibiting implantation. Exposure of target tissues to either hormone was suppressed during the m...

The study was conducted to evaluate the effect of Carraguard vaginal gel containing 0.75 mg of levonorgestrel (CARRA/LNG gel) administered in a single dose at different stages of follicle development over subsequent follicle rupture and hormonal levels. Randomized, blinded, cross-over study comparing the effects of a single administration of CARRA/...

A single injection of Estradiol (E2) given before mating accelerates egg transport (ET) in the rat oviduct via non transcriptional pathways involving cAMP, IP3 and protein kinases (PK), but does it via genomic pathways when it is given after mating. This change in signaling pathways induced by mating is referred to as “intracellular pathway shiftin...

All intrauterine devices (IUDs) that have been tested experimentally or clinically induce a local inflammatory reaction of the endometrium whose cellular and humoral components are expressed in the tissue and the fluid filling the uterine cavity. Depending on the reproductive strategy of the species considered and the anatomical features and physio...

The study was conducted to assess levonorgestrel (LNG) serum levels achieved after a single administration of two different doses of Carraguard vaginal gel containing LNG (CARRA/LNG), designed for use as microbicide and contraceptive for potential dual protection. This was a randomized double-blind pharmacokinetic study conducted in 12 subjects enr...

The oviducal transport of eggs to the uterus normally takes 72–96 h in the rat, but this is reduced to less than 20 h after a single injection of oestradiol (E2). This accelerated transport is associated with an increased frequency of pendular movements in the isthmic segment of the oviduct, with increased levels of the gap junction (GJ) component...

Although widely used, the mechanisms of action of the levonorgestrel emergency contraceptive pill (LNG ECP) are still unclear. There are increasing data to indicate that LNG is particularly effective as an ECP by interrupting follicular development and ovulation. An important outstanding question is whether it has any effect on fertilization or imp...

Levonorgestrel (LNG) consistently prevents follicular rupture only when it is given before the onset of the ovulatory stimulus. As locally synthesized prostaglandin (PG) plays a crucial role in follicular rupture and cyclooxygenase-2 (cox-2) catalyses the final step of PG synthesis, we reasoned that adding a cox-2 inhibitor to LNG would prevent fol...

Estradiol (E2) accelerates oviductal egg transport through nongenomic pathways involving oviductal protein phosphorylation in non-mated rats, and through genomic pathways in mated rats. Here we investigated the ability of cervico-vaginal stimulation (CVS) to switch the mode of action of E2 in the absence of other male-associated components. Pro-est...

La anticoncepción hormonal de emergencia (AHE) es uno de los pocos recursos que la mujer puede usar para prevenir un embarazo no deseado después de haber tenido una relación sexual en la que no usó método anticonceptivo o el que usó presentó una falla. Actualmente, el método preferido para la AHE es la píldora que contiene solamente levonorgestrel...

To compare mRNA and protein levels of proenkephalin A (PEA) and gamma-aminobutyric acid A receptor pi subunit (piGABA-R) in human secretory endometrium before and during receptivity and to determine the cell phenotypes where they are expressed. Prospective and observational, comparing prereceptive vs. receptive stages of secretory endometrium withi...

Successful implantation depends both on the quality of the embryo and on the endometrial receptivity. The latter depends on progesterone-induced changes in gene expression, a process that has been characterized by microarray analysis. One of the genes whose transcription appears to be enhanced during the receptive period is monoamine oxidase A (MAO...

This study was undertaken to determine whether 400 mg of prophylactic ibuprofen can alleviate pain from insertion of an intrauterine device (IUD) and to measure level of pain with improved techniques. We conducted a randomized, double-blind, placebo-controlled trial of 2019 first-time IUD users: 1008 women received placebo and 1011 women received 4...

Increased menstrual bleeding and pain are the primary side effects that lead to early removal of the copper intrauterine device (IUD). Ibuprofen and other non-steroidal anti-inflammatory drugs (NSAIDs) are proven treatments for such IUD-induced problems, but their effect on early IUD removal is unknown. A total of 2019 first-time IUD users were rec...

Emergency contraception is the only resource that women can use to avoid becoming pregnant after having sexual intercourse without contraceptive protection. It could be a powerful means to prevent unwanted pregnancies and their devastating consequences for women's health, social wellbeing and life project, and for the unwanted child, if all people...

The association of normal serum levels of immunoassayable gonadotrophins with anovulation during lactational amenorrhoea (LA) has not been fully explained. Serum FSH polymorphism was analysed in 10 women during LA between days 60 and 70 post-partum and again, in the mid-follicular phase (MFP), after resuming menstrual cyclicity. FSH microheterogene...

Comparisons of follicular development and hormonal profile in the same women during and after lactational amenorrhoea (LA) are scarce. We report follicular growth, pituitary and ovarian hormone serum levels in the same women during LA and in follicular phases after resumption of menstrual cyclicity. Serum samples were obtained from 10 women during...

Oestradiol (E(2)) accelerates oviductal transport of oocytes in cycling rats through a nongenomic pathway that involves the cAMP-PKA signalling cascade. Here we examined the role of the inositol triphosphate (IP3) and mitogen-activated protein kinase (MAPK) signalling cascades in this nongenomic pathway. Oestrous rats were injected with E(2) s.c. a...

Following infection with Neisseria gonorrhoeae, bacteria may ascend into the Fallopian tubes (FT) and induce salpingitis, a major cause of infertility. In the FT, interactions between mucosal epithelial cells and gonococci are pivotal events in the pathogen's infection cycle and the inflammatory response. In the current study, primary FT epithelial...

This study evaluates the performance of extended use of a progesterone (P)-releasing vaginal ring (PVR) in nursing women. An open-label, noncomparative study on the safety and contraceptive efficacy of PVR replaced every 4 months of use (instead of 3 months) in 192 PVR acceptors. PVR use was initiated at day 59+/-2 (mean+/-SD) postpartum and contin...

Few reports on the reproductive physiology of Cebus apella have been published. In this study we characterized menstrual cycle events by means of vaginal cytology, ultrasonography (US), and hormonal measurements in serum during three consecutive cycles in 10 females, and assessed the probability that ovulation would occur in the same ovary in conse...

In a multicenter 1-year trial of contraceptive vaginal rings (rings) involving 150 women, three dose combinations of the progestin Nestorone (NES) and ethinylestradiol (EE) were compared with respect to effectiveness, safety and acceptability. Mean in vitro drug release rates for the three doses were 150 and 15, 150 and 20 and 200 and 15 microg/day...

The morphologic changes undergone by the human secondary oocyte following ovulation were assessed by light microscopy in 57 specimens recovered from the Fallopian tube and endometrial cavity between 24 and 144 hr after the luteinizing hormone peak in plasma. Ovarecovered shortly after ovulation were surrounded by a large cumulus mass comprising app...

We assessed to what extent the standard dose of levonorgestrel (LNG), used for emergency contraception, or a single dose (half dose), given in the follicular phase, affects the ovulatory process during the ensuing 5-day period. Fifty-eight women were divided into three groups according to timing of treatment. Each woman contributed with three treat...

The aim of this study was to assess the participation of carbohydrate residues in the adhesion of spermatozoa to the oviductal epithelium in the rat. We first examined, by lectin labeling, the distribution of glycoconjugates in rat oviducts obtained under various hormonal environments. Several classes of glycoconjugates were abundant in the epithel...

A double-blind, placebo-controlled, randomized trial, was carried out in 120 Norplant users to evaluate the effect of mifepristone, 100 mg/day administered for 2 consecutive days every 30 days, on the vaginal bleeding pattern. Treatment was given from months 2-7 of implant use. Volunteers recorded bleeding and spotting days, during treatment and fo...

Experimental evidence to disprove the belief that emergency contraception with levonorgestrel (LNG) prevents pregnancy by interfering with post-fertilization events is lacking. Here we determined the effect of post-coital and pre-ovulatory administration of LNG on fertility and ovulation, respectively, in the Cebus monkey. To determine the effect o...

A 2-year trial of a single Nestorone (NES) rod implant was conducted at three Latin American centers, each enrolling 100 women. We studied the safety, effectiveness and acceptability of this progestin-releasing contraceptive implant. Three pregnancies occurred, the last at 18 months of use. Because no pregnancies were expected in the first 18 month...

The concept of luteal phase contraception and the use of mifepristone in clinical trials, which allows for testing of its validity, as well as clinical pharmacological research designed to understand its mode of action, are reviewed. Early luteal phase administration has a variety of morphological, physiological and biochemical effects on the endom...

The use of levonorgestrel (LNG) alone or combined with ethinylestradiol (Yuzpe regimen), for hormonal emergency contraception (HEC) has been approved in several countries whereas in others it is still under debate or has been rejected under the claim that these formulations abort the developmental potential of the embryo. The issue is whether they...

Several preparations of testosterone and its esters are being investigated alone or in combination with other gonadotropin-suppressing agents as possible antifertility agents for men. We studied the effectiveness of 7 alpha-methyl-19-nortestosterone (MENT) as an antispermatogenic agent in men. MENT has been shown to be more potent than testosterone...

Previously, we showed that oestradiol accelerates oviductal egg transport through a non-genomic action involving oviductal protein phosphorylation in non-mated rats, and through a genomic action in mated rats. Thus, sensory stimulation, seminal fluid or sperm cells may be the source of signals that switch the mechanism of action of oestradiol in th...

Levonorgestrel (LNG), a progestin widely used for regular hormonal contraception, is also used for emergency contraception (EC) to prevent pregnancy after unprotected intercourse. However, its mode of action in EC is only partially understood. One unresolved question is whether or not EC prevents pregnancy by interfering with postfertilization even...

This investigation examined the role of estrogen receptor (ER) on the stimulatory effect of estradiol (E2) on protein phosphorylation in the oviduct as well as on E2-induced acceleration of oviductal oocyte transport in cyclic rats. Estrous rats were injected with E2 s.c. and with the ER antagonist ICI 182 780 intrabursally (i.b.), and 6 h later, o...

Postcoital levonorgestrel does not disrupt post-fertilization events in rat

Infection of the Fallopian tubes (FT) by Neisseria gonorrhoeae can lead to acute salpingitis, an inflammatory condition, which is a major cause of infertility. Challenge of explants of human FT with gonococci induced mRNA expression and protein secretion for the proinflammatory cytokines interleukin (IL)-1α, IL-1β, and tumor necrosis factor alpha (...

A great deal is now known about the migration of spermatozoa within the female reproductive tract, and how they interact with the oocyte and achieve fertilization in a variety of species. The process involves a series of complex features. It is a mixture of active and passive transport and active migration, with drastic jumps in the numbers of sper...

This study was conducted to assess to what extent the Yuzpe regimen, or half the dose, given in the follicular phase, prevents ovulation during the ensuing 5 days. Sixty women were divided into six groups. All groups received placebo in one cycle and drug in another, in a randomized order. Groups differed by the dose and size of the leading follicl...

Intra-oviductal administration of RNA obtained from oviducts of estradiol-treated rats resulted in accelerated egg transport (Ríos et al., 1997). It is probable that estradiol-induced messenger RNA (mRNA) entered oviductal cells and was translated into the proteins involved in accelerated egg transport. In order to test this interpretation we depos...

Four different contraceptive implants for women, in the form of capsules or covered rods, that release either one of the synthetic progestins levonorgestrel, etonogestrel, Nestorone, or Elcometrine and nomegestrol acetate were considered. These progestins act by binding to their receptors located in diverse target cells, which are distributed along...

Intra-oviductal administration of RNA obtained from oviducts of estradiol-treated rats resulted in accelerated egg transport (Rios et al., 1997). It is probable that estradiol-induced messenger RNA (mRNA) entered oviductal cells and was translated into the proteins involved in accelerated egg transport. In order to test this interpretation we depos...

The objective of this study was to evaluate the contraceptive efficacy and clinical performance of a Nestorone subdermal implant (NES) in the postpartum period. NES (n = 100) and Copper T intrauterine device (T-Cu; n = 100) acceptors initiated contraception at 8 weeks postpartum and were followed at monthly intervals during the first year and at 3-...

Previously, we found that the dose of estradiol (E2) required to accelerate egg transport increases 5- to 10-fold, in mated compared to cyclic rats. Here we examined protein synthesis in the oviduct of mated and cyclic rats following a single injection of E2 known to accelerate oviductal egg transport or after concomitant treatment with progesteron...

In order to explore nongenomic actions of estradiol (E2) and progesterone (P4) in the oviduct, we determined the effect of E2 and P4 on oviductal protein phosphorylation. Rats on Day 1 of the cycle (C1) or pregnancy (P1) were treated with E2, P4, or E2 + P4, and 0.5 h or 2.5 h later their oviducts were incubated in medium with 32P-orthophosphate fo...

Prostaglandin-E(2) and platelet-activating factor (PAF) are embryonic-derived signals that time embryo passage into the uterus in the mare and hamster respectively. PAF-like activity is detectable in the spent media of preimplantation human embryos and it has been suggested that PAF may be the embryonic signal that controls embryo transport to the...

As it approaches the maternal surface, the attaching embryo encounters the epithelial glycocalyx, which contains the mucin, MUC1. A high density of MUC1 at the cell surface can inhibit cell adhesion. This raises the possibility of the existence of a uterine barrier to implantation that might allow maternal rejection of poorer quality embryos. To in...

Cebus apella is a New World monkey that has a menstrual cycle of 18-23 days with implantation at approximately luteal Day 5. The aim of this study was to characterize by lectin- and antibody-labeling the distribution of Muc1 and associated glycans on the endometrial and oviductal epithelium during the luteal phase of the cycle. Endometrial histolog...

To assess whether women who were administered the first injection of DMPA+E(2)C on day 7 of their menstrual cycle (delayed injection) exhibit the same degree of ovarian suppression as women who receive it on day 5 of their menstrual cycle. Multicenter, randomized controlled trial. Reproductive health clinics. Women aged between 18 and 38 years (inc...

Interaction of Neisseria gonorrhoeae with the oviductal epithelium in vitro was examined in 2 cm length segments obtained after surgical sterilization from users of copper T intrauterine device (IUD) or Norplant® and control women. Segments perfused with N.gonorrhoeae suspensions were incubated from 30 min up to 4 h, fixed, frozen and cut in 6–10 μ...

Estradiol accelerates oviductal embryo transport in the rat through changes of genomic expression in oviductal cells. However, the genes involved are unknown. We used a differential display by reverse transcription-polymerase chain reaction to detect estradiol (E2)-dependent genes in the rat oviduct. Rats on day 2 of pregnancy were untreated or tre...

The objective of this study was to evaluate the contraceptive efficacy and clinical performance of a Nestorone subdermal implant (NES) in the postpartum period. NES (n = 100) and Copper T intrauterine device (T-Cu; n = 100) acceptors initiated contraception at 8 weeks postpartum and were followed at monthly intervals during the first year and at 3-...

BACKGROUND: Prostaglandin-E 2 and platelet-activating factor (PAF) are embryonic-derived signals that time embryo passage into the uterus in the mare and hamster respectively. PAF-like activity is detectable in the spent media of preimplantation human embryos and it has been suggested that PAF may be the embryonic signal that controls embryo transp...

This 3-year study investigating the contraceptive efficacy and tolerability of Implanon in 635 volunteers demonstrates that it was well tolerated and had excellent, reversible, contraceptive efficacy. No pregnancies (Pearl index, 0; 95% CI 0.0-0.2) occurred during 1,200 woman-years of exposure. Irregular bleeding, mainly frequent and prolonged, was...

Contraceptive methods for breastfeeding women should be safe for the mother and infant and should not interfere with lactation. Progestin-only methods meet these conditions and can be used from the sixth week postpartum. Because all progestins are excreted in milk, those that are insufficiently active by the oral route are preferable to avoid any p...

Nestorone(R) progestin (NES) is a potent 19-nor-progesterone derivative which is biologically inactive when administered orally; however it is an excellent option for implant contraception. The objective of this study was to evaluate ovarian function during use of either one 4-cm or two 3-cm NES implants for 24 months. A total of 60 volunteers were...

Nestorone® progestin (NES) is a potent 19-nor-progesterone derivative which is biologically inactive when administered orally; however, it is an excellent option for implant contraception. The objective of this study was to evaluate ovarian function during use of either one 4-cm or two 3-cm NES implants for 24 months. A total of 60 volunteers were...