title: Changes in plasma steroid levels after single administration of hCG or LHRH agonist analogue in dog and rat.
abstract: The present study was designed to investigate the effect of acute administration of gonadotropin on testicular steroid secretion in dog and rat. Animals received a subcutaneous injection of 25 IU/kg of hCG or 1.5 microgram/kg of [D-Trp6, des-Gly-NH2(10)]LHRH ethylamide (LHRH-A). Testosterone is the predominant steroid measured, in dog plasma, under basal conditions. After LHRH-A injection, testosterone levels are not significantly changed while dehydroepiandrosterone and androst-5-ene-3 beta,17 beta-diol (delta 5-steroids) levels are stimulated by almost 20-fold (P less than 0.01). When dogs were injected with hCG, we also observed a marked stimulation of dehydroepiandrosterone levels (20-fold; P less than 0.01) accompanied by a small increase of plasma testosterone concentration (2-fold, P less than 0.01). In rats injected with either hCG or the LHRH analogue, an increment of plasma testosterone (7-fold, P less than 0.01) is detected in the first hour while plasma dehydroepiandrosterone levels are slightly stimulated. Moreover, in rats injected with hCG, low plasma steroid levels are present between 4-12 h after injection due to testicular desensitization. This marked decrease is then followed by a second peak of steroid secretion 24 h later. Acute testicular steroidogenic responsiveness to hCG on the dog is, however, different: after stimulation, the levels of plasma dehydroepiandrosterone are maintained at a plateau and slowly decline after 24-48 h. Our data indicate that in dogs, stimulation of testicular steroidogenesis leads to an increase of plasma delta 5-steroid levels while the same stimuli cause, in the rat, a stimulation of delta 4-androgen, particularly testosterone.
authors.forename: Y
authors.initials: Y
authors.lastname: Tremblay
authors.forename: A
authors.initials: A
authors.lastname: Belanger
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015114:Androstenediol / Q000097:blood; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D003687:Dehydroepiandrosterone / Q000097:blood; D004285:Dogs; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D051381:Rats; D013256:Steroids / Q000097:blood*; D013737:Testis / Q000378:metabolism; D013739:Testosterone / Q000097:blood; D013997:Time Factors; D017329:Triptorelin Pamoate / Q000031:analogs & derivatives*
chemical_list: D006063:Chorionic Gonadotropin; D013256:Steroids; D017329:Triptorelin Pamoate; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D003687:Dehydroepiandrosterone; C019176:Tryptal; D003994:Bucladesine; D015114:Androstenediol; D015056:1-Methyl-3-isobutylxanthine