Follicular dynamics and secretion of inhibin and oestradiol-17β during the oestrous cycle of the hamster

Abstract

Plasma and ovarian levels of inhibin were determined by a radioimmunoassay (RIA) at 3-h intervals throughout the 4-day oestrous cycle of hamsters. Plasma concentrations of FSH, LH, progesterone, testosterone and oestradiol-17 beta were also determined by RIAs. In addition, hamsters were injected at various times with human chorionic gonadotrophin (hCG) to determine the follicular development. The changes in plasma concentrations of FSH after injection of antisera to oestradiol-17 beta (oestradiol-AS) and inhibin (inhibin-AS) on the morning of day 2 (day 1 = day of ovulation) were also determined. Plasma concentrations of inhibin showed a marked increase on the afternoon of day 1, remained at plateau levels until the morning of day 4, then increased abruptly on the afternoon of day 4 when preovulatory LH and FSH surges were initiated. A marked decrease in plasma concentrations of inhibin occurred during the process of ovulation after the preovulatory gonadotrophin surges. An inverse relationship between plasma levels of FSH and inhibin was observed when the secondary surge of FSH was in progress during the periovulatory period. Plasma concentrations of oestradiol-17 beta showed three increase phases and these changes differed from those of inhibin. Changes in plasma concentrations of oestradiol-17 beta correlated well with the maturation and regression of large antral follicles. Follicles capable of ovulating following hCG administration were first noted at 2300 h on day 1. The number of follicles capable of ovulating reached a maximum on the morning of day 3 (24.8 +/- 0.6), and decreased by 0500 h on day 4 (15.0 +/- 1.1), corresponding to the number of normal spontaneous ovulations.(ABSTRACT TRUNCATED AT 250 WORDS)

A Simple Superovulation Method of A Single Injection of Follicle-Stimulating Hormone Combined with Equine Chorionic Gonadotropin for Superovulation of Suffolk Ewes During the Breeding Season: I. Effects of Different Treatments on the Endocrine Profiles.

“…The present findings are comparable with those of Yamada et al [12]. If the E 2 concentrations represent the number of maturing follicles [20], we can expect this simple superovulation method to result in ovulation and embryo recovery that are equal to those obtained with commonly used method with the multiple administration of pFSH combined with eCG.…”

Regulatory Role of Inhibin in Follicle-Stimulating Hormone Secretion and Folliculogenesis in the Guinea Pig.

“…The inhibitory effects of exogenous progesterone on folliculogenesis are demonstrated in cyclic rats through the hypothalamic-pituitary axis, especially via lowering serum LH [34]. The present results concerning with FSH secretion compare favorably with the results of passive immunization against inhibin in other animals, such as rats [26], hamsters [16,17], cows [14], mares [24] and sheep [21,36], implying passive immunization against inhibin can induce superovulation in guinea pigs. Inhibin has the ability to suppress FSH secretion by directly inhibiting expression of the gene encoding the FSH β subunit in the pituitary gland [3,22].…”

“…Passive immunization against inhibin can increase the secretion of FSH in female guinea pigs [29] as well as in the other animals [14,16,17,21,26]. However, the mechanism that regulates the onset and completion of the compensatory response to hemiovariectomy remains obscure in guinea pigs.…”

Cyclic changes in messenger RNAs encoding inhibin/activin subunits in the ovary of the golden hamster (Mesocricetus auratus)

“…Because expression of -subunit mRNA in granulosa cells increased as follicles developed, the increase in ovarian -subunit mRNA levels during the follicular phase is probably due to development of large follicles to be selected for ovulation. However, previous studies indicated that in the golden hamster, the ovary of day 3 was most abundant in healthy large follicles, and the number of healthy large follicles decreased from day 3 to the morning of day 4 (Greenwald 1991, Kishi et al 1995. Therefore, -subunit mRNA levels do not reflect merely the number of large healthy follicles.…”

“…For example, the corpus luteum in the cyclic ovary always begins to show signs of histological regression by 3 days after ovulation and almost completely vanishes by the next ovulation (Grady & Greenwald 1968). In addition, the follicle-stimulating hormone (FSH) surge during the periovulatory period is clearly separated into two peaks in the golden hamster (Bast & Greenwald 1974, Kishi et al 1995 unlike the rat in which the FSH surges almost overlap (Watanabe et al 1990).…”