Article

Endocrine Mechanisms Responsible for Different Follicular Development During the Estrous Cycle in Hatano High- and Low-avoidance Rats

Primate Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
Journal of Reproduction and Development (Impact Factor: 1.52). 08/2011; 57(6):690-9. DOI: 10.1262/jrd.10-160S
Source: PubMed

ABSTRACT

Hatano high- and low-avoidance rats (HAA and LAA strains, respectively) were selected and bred according to the avoidance rate in a shuttle-box task. Although they have clear strain differences in ovarian function, their endocrine mechanisms still remain to be clarified. Differences in female reproductive endocrinology between the strains were investigated by means of measuring the plasma concentration of reproductive hormones during the estrous cycle. LAA rats showed approximately threefold lower basal and surge levels of LH, a more than fourfold lower level of FSH surges and higher levels of inhibin A and inhibin B during the estrous cycle compared with the levels seen in HAA rats. The concentration of estradiol-17β in the proestrous stage was significantly lower in LAA rats than in HAA rats. Additionally, LH and FSH secretions from primary cultured anterior pituitary cells with or without in vitro GnRH stimulation were lower in the cells derived from LAA rats and, in terms of FSH secretion, were unresponsive to GnRH in contrast to cells derived from HAA rats. Although an increased number of preantral follicles in diestrus were observed in LAA rats, number of hCG-induced ovulation was lower in LAA rats. LAA rats may have much more follicle growth during the early stage of folliculogenesis, but most follicles might not grow into mature follicles. These results strongly suggest that the strain difference in ovarian function of these two Hatano rats is due to the difference in the regulation of hypothalamo-hypophyseal system for gonadotropins secretion.

Download full-text

Full-text

Available from: Sayaka Akieda-Asai, Jan 22, 2015
  • Source
    • "Serum FSH and LH levels were determined using the National Institute of Diabetes and Digestive and Kidney disease (NIDDK) kit for rat FSH and LH (Baltimore, MD, USA) as described previously [26]. Iodinated preparations used in this study were rat FSH-I-7 and rat LH-I-7, and the antisera were anti-rat FSH-S11 and antirat LH-S10, respectively. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This study aims to delineate the relationship among estrogen deficiency, neurodegeneration, and cognitive impairment of ovariectomized rats. Female Sprague-Dawley rats were ovariectomized and euthanized after 1-4month periods (M(0)-M(4) groups). Blood samples were collected for the determination of serum levels of 17β-estradiol (E(2)), luteinizing hormone (LH), and follicle stimulating hormone (FSH). Five consecutive days before the euthanization, cognitive performance of the rats was examined by Morris water maze test. After euthanization, the hippocampus was collected, and expression of the genes associated with amyloid plaques (App, Adam10 and Bace1) and neurofibrillary tangles (Tau4 and Tau3) were examined by real-time PCR. Serum E(2) levels were declined following 2weeks of ovariectomy. Conversely, serum FSH and LH levels were profoundly increased by 2weeks of ovariectomy for approximately 4 and 22 times, respectively. Cognitive impairments, indicated by the longer latency and distance, were observed only in the M(3) and M(4) groups. The Tau4 mRNA levels were significantly increased as early as 1month after ovariectomy (in the M(1) group; P<0.05), and tended to be increased further with the advancing time. Similarly, the Tau3 mRNA levels were increased by ovariectomy, but with the highest level in the M(1) group, and decreased thereafter. The mRNA levels of App, Adam10 and Bace1 were increased by ovariectomy, but significant differences were observed only in the M(4) group. These results indicate that estrogen deficiency can induce a sequence of events that results in the production of neurofibrillary tangles, amyloid deposition, and spatial memory deficit in rats.
    Full-text · Article · Oct 2013 · General and Comparative Endocrinology
  • [Show abstract] [Hide abstract]
    ABSTRACT: A one-lifespan test was carried out to establish a test protocol for endocrine-disrupting chemicals (EDCs). Diethylstilbestrol was administered by oral gavage to neonatal rats at doses of 0.05, 0.5 and 5 μg/kg/day for 5 days after birth. Abnormal estrous cycles were observed throughout the study in all females from the 5 μg/kg group, and in 40% from the 0.5 μg/kg group from 24 weeks of age. The conception rate of 12-week-old females in the 5 μg/kg group was 0%, and that of the 23-week-old females in the 0.5 μg/kg group was 33.3%. No effect of DES was observed at the first parturition in any group, except for the 5 μg/kg group. However, litter size was significantly reduced in the 0.5 μg/kg group at the second parturition. These results indicated that a prolonged period of observation of reproductive function is necessary to determine EDCs reliably.
    No preview · Article · May 2012 · Reproductive Toxicology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Differences in reproductive endocrinology distinguish Hatano high-avoidance animals (HAA) from low-avoidance animals (LAA). Compared to HAA rats, female LAA rats secrete low levels of basal luteinizing hormone (LH) and a reduced LH surge. To investigate the underlying cause of the differences between the two strains, levels of the following mRNAs were measured in the hypothalamus of intact and ovariectomized (OVX) females treated with vehicle control or estradiol-17β (E2): gonadotropin-releasing hormone (Gnrh), newly isolated rat kisspeptin (Kiss)1 mRNA variant-1 (Kiss1V1) and variant-2 (Kiss1V2) and estrogen receptor (Er) α. In OVX-HAA rats, the levels of Gnrh mRNA in the preoptic area (POA) 30 hours after E2 treatment were significantly higher than in OVX-LAA rats. For HAA rats, the levels of Kiss1V1 and Kiss1V2 mRNA in the anteroventral periventricular nucleus (AVPV) were significantly higher in the E2-treated group than in the vehicle-treated group. In the arcuate nucleus (Arc) of HAA rats, Kiss1V1 and Kiss1V2 expression was significantly lower in E2-treated females compared to vehicle-treated females. Kiss1V2 expression was significantly higher than Kiss1V1 expression in intact HAA rats. In E2-treated OVX-LAA rats, there were no changes in the expression levels of Gnrh, Kiss1V1 or Kiss1V2. In intact LAA rats, no differences were observed in the expression levels of Kiss1V1 or Kiss1V2 in the AVPV, but the expression levels of these mRNAs in the Arc were significantly lower in E2-treated OVX-LAA rats. Additionally, no strain differences were observed for Erα mRNA expression in either the AVPV or Arc. These results indicate that the failure of estrogenic regulation of GnRH neurons in the POA and of kisspeptin neurons in the AVPV of LAA rats causes low LH secretion and reduced reproductive function.
    No preview · Article · Oct 2012 · General and Comparative Endocrinology
Show more