Abstract
In the present study, we investigated changes in plasma concentrations of inhibin, estradiol-17β, progesterone and FSH in the golden hamster (Mesocricetus auratus) superovulated by equine chorionic gonadotropin (eCG) treatment. In addition, the hamsters were injected at various times with human chorionic gonadotropin (hCG) to determine the follicular development after treatment with eCG. After treatment with 30 IU eCG at 1100 h on day 1 of the estrous cycle (day 1=day of ovulation), superovulation (36.5 ± 1.1 v.s. 13.5 ± 0.4 in controls treated with saline) occurred on the expected next day 1. Plasma concentrations of inhibin and estradiol-17β increased and plasma concentrations of FSH decreased in the animals given 30 IU eCG. Plasma concentrations of progesterone also increased after eCG treatment; however, they decreased to control levels within 48 h after eCG injection. The number of follicles capable of ovulating after hCG administration was dramatically increased within 36 h after eCG injection (43.4 ± 3.4). Thereafter, the number of follicles capable of ovulating decreased to about a half of the peak value during the next 6 h period, then increased gradually to the numbers of ovulations observed on the next day 1. Plasma inhibin and estradiol-17β were augmented and plasma concentrations of FSH were suppressed in the animals in which follicular development was stimulated, though there is a difference in the changing pattern between plasma inhibin and estradiol-17β. The present results also suggest that plasma concentrations of inhibin may be an indicator for the number of developing follicles and estradiol-17β may be an indicator for follicular maturation.
