Induction of superovulation by immunoneutralization of endogenous inhibin through the increase in the secretion of follicle-stimulating hormone in the cyclic golden hamster

Abstract

The present study was conducted to study the effect of immunoneutralization against endogenous inhibin on FSH, LH, oestradiol-17 beta and progesterone secretion and to investigate the effect of removal of endogenous inhibin on subsequent follicular development in the hamster. After treatment with anti-inhibin serum (inhibin-AS) at 1100 h on day 2 of the oestrous cycle (day 1 = day of ovulation), a marked increase in plasma levels of FSH and a slight increase in plasma levels of LH were noted and pituitary contents of FSH, but not LH, were also increased. In the group treated with inhibin-AS, superovulation occurred on day 1 of the following cycle. Plasma levels of oestradiol-17 beta markedly increased with the increase in the number of ovulations induced by human chorionic gonadotrophin (hCG) as compared with those in control animals. In the second cycle, plasma concentrations and pituitary contents of FSH in the animals given 200 microliters inhibin-AS still showed high values as compared with those in the animals treated with control serum, although superovulation did not occur on day 1 of the third cycle. Plasma concentrations and pituitary contents of LH in the hamster given 200 microliters inhibin-AS tended to decrease as compared with those in control animals during the second cycle. Plasma concentrations of oestradiol-17 beta in the animals treated with 200 microliters inhibin-AS changed in a similar way to controls. A marked increase in plasma concentrations of progesterone was noted on days 1 and 2 of the second cycle in the group receiving inhibin-AS. The twice daily injection of 1 IU hCG during the second cycle to the animals given 200 microliters inhibin-AS induced superovulation on day 1 of the third cycle. These results indicate that circulating inhibin may be an important indicator of the number of developing follicles and may maintain the species-specific number of developing follicles through suppression of FSH secretion in the cyclic hamster. They also suggest that high levels of inhibin slightly suppress plasma levels of LH, indicating that plasma LH may also regulate follicular development in the cyclic hamster.

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.…”

Roles of the Basal Level of LH and FSH in the Regulation of Follicular Development during Pseudopregnancy in the Rat.

“…The LHRH-AS administration produced an increase in plasma FSH levels without altering plasma prolactin levels, whereas the procedure resulted in a marked decline in both plasma LH levels and the number of follicles capable of ovulating in response to hCG. In addition, the number of ovulating follicles was restored to the control value with a gradual increase in plasma LH levels reported not only in pregnant [10,19,20], lactating [11][12][13] and immature rats [21] but also in cycling rats [22] and hamsters [23]. The present results collectively indicate that the basal secretion of LH is also responsible for the follicular development and maintenance during pseudopregnancy of the rat.…”

Immunizing Norduz goats against inhibin

“…Low number of ovulated follicle, despite more developing ones, may be attributed to this effect in immunized goats (Medan et al 2003 b ). Same results were observed in hamsters treated with inhibin antiserum (Kishi 1996) and also in other species. Inhibin immunization improves markedly follicle development and oestradiol secreted by follicles.…”