Acute desensitization of pituitary FSH response to LHRH in ovariectomized rats: further evidence that in the presence of ovarian proteins the LHRH-dependent, LH-like component of FSH release becomes apparent.
Pulsatile release of LHRH and short-term pituitary desensitization to LHRH in the rat are believed to be necessary for the maintenance of LH pulsatility. In contrast, FSH release is partly induced by LHRH release and is partly LHRH-independent. This LHRH-independent release of FSH is subject to inhibitory feedback control by ovarian proteins (probably inhibin), and may obscure an LHRH-induced short-term loss of pituitary FSH responsiveness to LHRH. The object of this study was to establish whether short-term pituitary desensitization to single doses of LHRH results not only in a loss of LH response, but also of FSH response. Ovariectomized rats were used to eliminate the influence of steroid feedback. A group of ovariectomized rats was pretreated with steroid-free bovine follicular fluid (bFF) to suppress LHRH-independent FSH release, and phenobarbital to suppress LHRH-dependent FSH release respectively, 7 and 1 h before administration of LHRH. Another group received phenobarbital only. The animals were injected sequentially with either low or high doses of LHRH (1.25 or 10 ng/100 g body weight at times 0 and at 80, 120 or 180 min, and 6.25 or 50 ng/100 g at 60 min). Blood was taken for FSH measurements before and 5 and 10 min after each injection. Rats pretreated with bFF and phenobarbital showed an acute FSH response related to the dose of injected LHRH. No dose-response curve was seen in animals which had only been pretreated with phenobarbital.(ABSTRACT TRUNCATED AT 250 WORDS)
Lambalk
C B
CB
Department of Pharmacology, University of Leiden, The Netherlands.
van Rees
G P
GP
Schoemaker
J
J
de Koning
J
J
van Dieten
J A
JA
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000378:metabolism*; D015571:Follicular Fluid; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000378:metabolism; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology*; D010634:Phenobarbital / Q000494:pharmacology; D010902:Pituitary Gland / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D010634:Phenobarbital