Evidence for ovarian “inhibin”: Suppression of the secondary rise in serum follicle stimulating hormone levels in proestrous rats by injection of porcine follicular fluid

Abstract

Margoliash, September 20, 1977 ABSTRACT The present studies were carried out to see if porcine follicular fluid could inhibit increases in serum follicle stimulating hormone (FSH) levels when injected into the rat. For these studies the pentobarbital-treated proestrous rat was chosen as the major test animal model. If an artificial surge of luteinizing hormone (LH) is administered to these rats, it can induce a synchronized secondary rise in FSH secretion rate. Normal saline-treated rats were also used as test animals. They exhibit preovulatory endogenous "surges" of LH and FSH, and also a secondary FSH rise.Porcine follicular fluid was harvested from medium-sized and large (3-to 10-mm diameter) follicles and treated with charcoal to remove endogenous steroids. Charcoal-treated porcine serum served as a control solution. The fluid was injected intraperitoneally in two 0.5-ml doses into pentobarbital-treated proestrous rats immediately and 3 hr after LH injection. Follicular fluid, but not the serum, suppressed the secondary, LH-induced FSH rise (P < 0.01) in a dose-dependent manner, without altering the effects of LH upon serum ovarian steroid levels or follicular rupture. It was effective down to a total dose of 200 Al. Porcine follicular fluid also blocked the secondary FSH surge in normal proestrous rats exhibiting endogenous LH/FSH primary surges. Thus, it would appear that porcine follicular fluid contains a non-steroidal substance~s) that can block the secretion of FSH that is secondary to a natural or artificial LH surge.

Inhibiting activin-A signaling stimulates bone formation and prevents cancer-induced bone destruction in vivo

“…Activins and inhibins were first identified as important regulators of pituitary follicle-stimulating hormone release. (14)(15)(16)(17) Subsequent studies have demonstrated that activins are expressed in diverse tissues and play important roles in embryology, wound healing, and tissue homeostasis. (18)(19)(20)(21)(22) Activins signal by binding either the activin receptor type IIA (ActRIIA) or the activin receptor type IIB, which recruits the type I receptor, activin-like kinase 4 (Alk4), leading to phosphorylation of cytoplasmic Smads 2/3.…”

Activin and inhibin receptor gene expression in the ewe pituitary throughout the oestrous cycle

“…This hypothesis is supported by an inverse relationship between plasma concentrations of inhibin and FSH during the periovulatory period (Kimura et al 1983, Hasegawa et al 1989, Watanabe et al 1990, Woodruff et al 1996. In addition, administration of an inhibin preparation or recombinant human inhibin A in the rat abolishes the rise of FSH during oestrus (Schwartz & Channing 1977, Rivier & Vale 1991. In contrast, the blockade of GnRH does not eradicate the secondary surge of FSH in the rat.…”

Oocyte maturation inhibitor, inhibin and steroid concentrations in porcine follicular fluid at various stages of the oestrous cycle

“…Porcine follicular fluid also contains a factor that specifically inhibits the secretion of FSH from the pituitary gland (Schwartz & Channing, 1977;Welschen, Hermans, Dullaart & de Jong, 1977). This factor is produced by granulosa cells (Erickson & Hsueh, 1978;Hermans, van Leeuwen, Debets, Sander & de Jong, 1982), and has an action which is identical to that of inhibin in the male (de Jong & Sharpe, 1976).…”