The Journal of Reproduction and Development Supplement

It has been suggested that the circadian clock operates in the extensive peripheral tissues as well as in the suprachiasmatic nucleus. The present study was performed to examine the operation of circadian clock in the ovary, thereby providing insights into how the circadian clock is possibly involved in the ovarian physiology including follicular development and luteinization. The operation of circadian clock in the rat ovary was investigated employing the immunohistochemistry and RT-PCR methods, the cell culture (normal and Per2-dLuc transgenic) system and real-time monitoring of promoter activity. The Per2 promoter connected with destabilized luciferase (dLuc) was introduced in the transgenic rats. The result showed that PER1 was non-cyclic in the developing follicles over a 24-h time course, while obviously rhythmic in the corpora lutea. Furthermore, gonadotropins significantly stimulated Per1 expression via CREB in granulosa cells, but not in luteal cells. Using Per2-dLuc transgenic cells, the working capabilities of the clock system were compared in granulosa and luteal cells. After dexamethasone synchronization, only one cycle of Per2-dLuc oscillation was observed in granulosa cells within 96 h monitoring, while persistent oscillation was sustained in luteal cells. Additionally, EGF and bFGF, but not IGF-I, reinforced the sustaining capability of the clock system in granulosa cells. It is thus supposed that, during follicular development, gonadotropins may be the potent factors disrupting normal circadian clockwork by constitutive regulation of Per1 via CREB and induced cell differentiation.

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Hatano high- and low-avoidance rats (HAA and LAA) were selected and bred according to their responses on a shuttlebox task. Previous studies have shown clear strain differences in secretion of gonadotropins (Gns) and steroid hormones during the estrous cycle as well as avoidance behavior. This study was designed to measure circulating inhibin A and B and to correlate Gns, steroid hormones, and ovarian folliculogenesis. Inhibin B was elevated from the day of metestrus and declined gradually through proestrus in both strains. Additionally, inhibin B declined most at 0600 h on the day of estrus. Indeed, LAA showed higher levels of inhibin B than HAA throughout the estrous cycle. Circulating inhibin A, however, was low on the day of metestrus and increased through the afternoon of proestrus in both strains. In addition, LAA showed higher levels of inhibin A than HAA during the late evening of proestrus and early morning of estrus. However, inhibin A and B was inversely correlated with FSH surge in both strains. The presence of small follicles at 1200 h on the day of metestrus and diestrus were greater in LAA, although antral follicles were lower in LAA rats as compared with HAA. These results strongly suggest that inhibin B is secreted from developing small follicles, whereas inhibin A is secreted from mature antral follicles. Thus, the increase in circulating inhibin B and decrease in circulating FSH may be due to acceleration of follicular growth in LAA. In addition, LAA may grow more follicles during the early stage of folliculogenesis, although many may not growth to maturity. Supported in part by a Grant-in-Aid for COE (E-1) and Basic Scientific Research (B-18310044).

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Pueraria mirifica (PM) has been interested because of phytoestrogens contained in its roots, showing female hormone like effects. From the study of non-human primate, Macaca fascicularis, after a single feeding of 1,000 mg of PM (PM-1,000), the length of menstrual cycles were prolonged in adult monkeys, but the doses of 10 and 100 mg of PM (PM-10 and PM-100) could not change menstrual cycle lengths. The serum patterns of follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), or progesterone (P) in all two entire menstrual cycles did not change in all monkeys after treatment with PM-10, PM-100, or PM-1,000, when compared with those of pre-treatment. In the study of daily treatment of PM-10, PM-100, or PM-1,000, the menstrual cycle lengths were prolonged significantly during PM-10 and PM-100 treatments, and stopped completely throughout the PM-1,000 treatment and post-treatment periods. Serum FSH, LH, E2, and P levels were suppressed during treatment in a dose-dependent manner. During the post-treatment period, changes of menstrual cycle length and suppressed hormonal levels could recover in PM-10 and PM-100 groups, but could not recover in PM-1,000 group. Similarly, serum FSH, LH, and E2 levels were also suppressed in aged menopausal monkeys treated with PM-10, PM-100, and PM-1,000 for 90 days. From these results, it was assumed that phytoestrogens contained in PM acted as estrogen and suppressed the hypothalamus and/or pituitary functions by reducing the secretion of GnRH, FSH, and LH, then suppressed the secretion of sex steroid hormones in both adult and aged monkeys. In conclusion, PM influence reproduction by estrogenic action of phytoestrogens.

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[Objective] To investigate the effects of interval between calving and first ovulation on ovarian cycles postpartum and conception rate in high-producing dairy cows. [Methods] Days of first ovulation postpartum and subsequent ovarian cycles until cows diagnosed pregnant were monitored by milk progesterone profiles in a commercial dairy herd with 60 Holstein-Friesian cows with average milk yield per cow per lactation of 10,200kg. Incidence of abnormal ovarian cycles was calculated as percentage of abnormal cycles in total cycles during an observation period in each cow. [Results] Of 53 cows examined, percentages of cows which ovulated 1-14 d, 15-20 d, 21-35 d, 36-60 d, and >60 d postpartum were 28.3%, 26.4%, 30.2%, 13.2 %, and 1.9%, respectively. Incidences of abnormal ovarian cycles during pre-service and service periods in 45 cows with early (1-35d) first ovulation and 8 cows with late (U>/U36d) first ovulation were 33.9% and 36.2%, respectively. Percentages of ovarian cycles with prolonged luteal phase were 22.3% in cows with early first ovulation and 13.8% in those with late first ovulation. First AI conception rate and pregnancy rate within 100 d postpartum in cows with early first ovulation were higher than cows with late first ovulation (26.5% vs 0% and 28.9% vs 0%, P<0.01). [Conclusion] Interval between parturition and first ovulation postpartum did not adversely affect subsequent ovarian cycles. However, cows with early first ovulation tended to have a higher incidence prolonged luteal phase than those with late first ovulation. Delayed first ovulation postpartum adversely affected reproductive performance.

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