title: Pituitary-testicular function is suppressed by an LHRH antagonist but not by an LHRH agonist in the marmoset monkey.
abstract: The use of pituitary desensitization by an LHRH agonist (buserelin) to examine pituitary-testicular function was investigated in a New World primate. Six adult male marmoset monkeys were injected s.c. with an LHRH agonist implant (1.5 mg in a rod 0.5 cm long). Pharmacokinetics, determined by radioimmunoassay of urinary buserelin, revealed a rapid initial release of the agonist followed by a steady decline during a 200-day period. The LHRH agonist treatment resulted in a rapid initial rise in plasma LH followed by a return to mean values similar to those seen in the control samples by 7 days after implantation. Using the present protocol, no evidence of subsequent pituitary desensitization or suppression of testicular function was observed, plasma concentrations of LH and testosterone remaining within the normal range during the 200-day study period. In contrast, pituitary-testicular function was suppressed in the male marmoset after blockade of pituitary LHRH receptors by an LHRH antagonist. Five adults were treated with a single s.c. injection of the antagonist [Ac-D-Nal(2)1,D-pCl-Phe2,D-Trp3,D-Ser(Rha)6,AzGlyNH2(10)]-LHRH at a dose of 300 micrograms/kg. The LHRH antagonist induced a marked suppression of plasma LH and testosterone by 6-8 h, the low levels being maintained for 24-48 h. These results show that, whereas treatment with an LHRH antagonist can inhibit pituitary-testicular function in the male marmoset, it may be that desensitization cannot be induced by the LHRH agonist used.
authors.affiliation: MRC Reproductive Biology Unit, Centre for Reproductive Biology, Edinburgh.
authors.forename: S F
authors.initials: SF
authors.lastname: Lunn
authors.forename: A F
authors.initials: AF
authors.lastname: Dixson
authors.forename: J
authors.initials: J
authors.lastname: Sandow
authors.forename: H M
authors.initials: HM
authors.lastname: Fraser
mesh_terms: D000818:Animals; D002064:Buserelin / Q000493:pharmacokinetics / Q000494:pharmacology; D002144:Callithrix / Q000097:blood / Q000502:physiology*; D002143:Callitrichinae / Q000502:physiology*; D003864:Depression, Chemical; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011966:Receptors, LHRH / Q000187:drug effects; D013737:Testis / Q000187:drug effects* / Q000502:physiology; D013739:Testosterone / Q000097:blood
chemical_list: D011966:Receptors, LHRH; C065080:LHRH, Ac-2-Nal(1)-4-Cl-Phe(2)-Trp(3)-Ser(Rha)(6)-AzGlyNH2(10)-; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D007986:Luteinizing Hormone; D002064:Buserelin