Submission Number: KAZ-4-10-26

Abstract Number: 148

FOLLICULAR DYNAMICS AND SECRETION OF INHIBIN A, INHIBIN B AND ACTIVIN A DURING THE LATE PREGNANCY IN THE GOLDEN HAMSTER.

Kenichi Ohshima ^1,2, H Kishi ³, M Itoh ⁴, Gen Watanabe* ¹, Koji Y Arai ², Katsuhiko Arai ², Kohkichi Uehara ², NP Groome ⁵ and Kazuyoshi Taya* ¹

Laboratory of Veterinary Physiology, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan ¹
Department of Tissue Physiology, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan ²
Department of Animal Reproduction, National Institute of Animal Industry, Ibaraki, 305-0991, Japan ³
Primate Research Institute, Kyoto University, Aichi 484-8506, Japan ⁴
School of Biological and Molecular Sciences, Oxford Brookes University, Headington Oxford, United Kingdom OX3 0BP ⁵

Abstract:
During late pregnancy in the golden hamster, marked increase in ovarian estradiol-17 beta secretion coincides with increasing number of large healthy follicles. Thereafter, all large antral follicles degenerate by term, and do not reappear until the end of lactation. The mechanism of this follicular dynamics during the late pregnancy remain to be determined. To investigate the follicular dynamics during the late pregnancy, secretion of inhibin A, inhibin B and activin A were investigated. Plasma concentrations of inhibin A, inhibin B and activin A were determined by ELISA from day 8 of pregnancy (day of sperm positive = day 0 of pregnancy) to day 0 of lactation (day of delivery). Gonadotropins and steroid hormones were also determined by RIA. Plasma concentrations of inhibin A and inhibin B abruptly increased from day 8 and reached the maximum level on day 10 of pregnancy. Thereafter, plasma concentrations of inhibin A and inhibin B gradually decreased by the day of delivery. Plasma concentrations of activin A gradually increased from day 8, and reached a maximum level on day 15 of pregnancy, followed by an abrupt decrease at the delivery. The number of ova shed in response to 10 IU hCG abruptly increased from day 8 (15.8 1.5) to day 10 (33.2 3.2) of pregnancy, and the number of large healthy follicles were maintained until day 14 of pregnancy, followed by an abrupt decline by day 0 of lactation. Changes in plasma levels of inhibin A and inhibin B were parallel with a number of large antral follicles in the ovary. Plasma concentrations of FSH and LH were maintained at the base level during the period studied. Abrupt declines in plasma inhibin A and inhibin B were observed after ovariectomy, whereas removal of placentae or hysterectomy caused an abrupt decline in plasma activin A. These results clearly indicate that inhibin A and inhibin B are secreted from large healthy follicles, whereas activin A is mainly secreted from placenta and uterus during the late pregnancy in the golden hamster. These results suggest that a large amount of activin A may be involved in the regulation of follicular development. This work was supported by US-Japan cooperative Research Grant from the Japan Society for Promotion of Science. .

Keywords: inhibin, activin, pregnancy, hamster, follicular development

This abstract is being presented at: 8:00 AM in session:
Follicular Development I