Effect of follicular fluid and inhibin immunoneutralization on FSH-induced preovulatory follicle growth in the ewe

Abstract

The potential direct ovarian effects of immunoneutralization of inhibin, which increases, and follicular fluid treatment, which inhibits, follicle development in normal ewes was investigated in a sheep model in which endogenous FSH and LH secretion was suppressed thus removing any potential effects of treatment-induced alterations in endogenous FSH or LH secretion. Eighteen Welsh Mountain ewes were treated with two agonist implants containing 3.3 mg buserelin giving a total of 6.6 mg buserelin per animal. During week 5 of treatment all ewes were given a 72-h continuous infusion of ovine FSH (5 micrograms/h) starting at 09.00 h. Six ewes were treated with antiserum to the 1-26 alpha peptide fragment of porcine inhibin 0 h and 24 h after the start of the FSH infusion, and a further six ewes were treated with charcoal-stripped ovine follicular fluid (oFF) as a source of inhibin, at 09.00 and 17.00 h throughout the 72 h of FSH infusion. The plasma concentrations of both FSH and LH were significantly reduced in all ewes after 5 weeks of treatment with buserelin, and no large follicles greater than 2.5 mm in diameter were present. Treatment with inhibin antiserum or oFF had no effect, compared with control ewes, on the plasma concentrations of either FSH or LH during the FSH infusion period. After 72 h of FSH infusion there was no difference in the number of small follicles (less than 2.5 mm in diameter) or large follicles (greater than 2.5 mm in diameter) or the size of the largest follicles between control ewes and ewes treated with either inhibin antiserum or oFF.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of active immunization of sheep against an amino terminal peptide of the inhibin alpha C subunit on intrafollicular levels of activin A, inhibin A and follistatin

“…As such, the study provides evidence that long-term exposure to inhibin antibodies may have direct effects on granulosa cell function that are not mediated by changes in pituitary FSH secretion. This evidence contrasts with a previous study in which acute exposure to exogenous inhibin (oFF) or inhibin antiserum had no effect on FSH-induced follicular growth in gonadotrophin-releasing hormone (GnRH) agonistsuppressed sheep (McNeilly et al 1991). However, other studies (Cahill et al 1985a,b) have shown that exogenous inhibin (oFF) can reduce gonadotrophin-induced follicle development in both intact and hypophysectomized ewes, findings which are more supportive of a direct ovarian action of inhibin.…”

“…It should be emphasized that the present study concerns the long-term (>1 year) consequences of active immunization against inhibin, and that these are likely to be quite different from the acute effects on the pituitary-ovarian axis resulting from passive immunization against inhibin (Mann et al 1989, 1993, McNeilly et al 1991. The results confirm and extend previous evidence (Knight et al 1991b, Fray et al 1994, Bleach et al 1996 suggesting that the long-term stimulatory effect of IMM on follicle development may not be due exclusively to neutralization of the negative feedback action of inhibin on pituitary FSH.…”

Characterization of persistent follicles induced by prolonged treatment with progesterone in dairy cows: An experimental model for the study of ovarian follicular cysts

“…To validate the electrochemiluminescence immunoassay and RIA of steroids, pooled follicular fluid and serum of ovariectomized cows were made steroid free by charcoal treatment [29]. Serial dilutions of estradiol, testosterone, progesterone, and 17-hydroxyprogesterone (Sigma-Aldrich) were prepared by using steroid-free follicular fluid or serum as diluents.…”

Mouse Ovarian Follicles Secrete Factors Affecting the Growth and Development of Like-Sized Ovarian Follicles In Vitro1

“…Selection of follicles is thus considered to be a systemically controlled process, regulated by the action of gonadotropins (primarily FSH), and modulated by intrafollicular factors such as IGF and its binding proteins [3][4][5]. However, although there is compelling evidence for this indirect, endocrine loop [2,6,7], and although it can explain how subordinate follicles fail to complete development, it is less clear how such a system could ensure that only the correct, species-specific number of follicles become dominant within the ovary in the first instance.…”