Effects of ovarian inhibin on pulsatile release of gonadotrophins and secretion of LHRH in ovariectomized rats: evidence against a central action of inhibin.
Intraperitoneal administration of bovine follicular fluid (bFF) decreased plasma concentrations of FSH in ovariectomized rats after 2-3 h, while plasma LH and prolactin were unaffected. In untreated ovariectomized animals the concentrations of these hormones were found to show pulsatile variations. Concomitant occurrence of peak values of LH and FSH was found in about 40% of the pulses. No pulses of FSH were observed after i.p. treatment with bFF or partly purified preparations of inhibin from bFF, but the pulsatile release of LH and prolactin remained similar. Infusion of bFF into the lateral ventricle of the brain did not alter the concentrations of FSH, whereas administration of bFF into the pituitary gland diminished the plasma concentrations of FSH. Anaesthesia (urethane plus xylazine) did not prevent the occurrence of the pulses of FSH and LH, but it reduced the pulse amplitude and clearance. During this anaesthesia, the concentrations of LHRH in the hypophysial stalk plasma decreased by 30% after administration of bFF, but did not alter after treatment with partly purified preparations of inhibin. It is concluded that the inhibin-like activity in bFF suppresses pulsatile FSH secretion in ovariectomized rats by an action on the pituitary gland, but has no effect on the pulsatile release of LH and prolactin.
de Greef
W J
WJ
Eilers
G A
GA
de Koning
J
J
Karels
B
B
de Jong
F H
FH
D000818:Animals; D001826:Body Fluids / Q000378:metabolism; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D007265:Inhibins / Q000494:pharmacology*; D007276:Injections, Intraventricular; D006080:Ovarian Follicle / Q000378:metabolism*; D010052:Ovariectomy; D010902:Pituitary Gland; D051381:Rats
D006065:Gonadotropins, Pituitary; D007987:Gonadotropin-Releasing Hormone; D007265:Inhibins