Blockade of singular follicle-stimulating hormone secretion and testicular development in photostimulated Djungarian hamsters (Phodopus sungorus) by a gonadotropin-releasing hormone antagonist.
Photostimulated male Djungarian hamsters following placement in a long-day photoperiod exhibit a characteristic rise in serum FSH levels that occurs in the absence of a simultaneous rise in LH levels. It is not known whether this singular FSH secretion is dependent upon a differential responsiveness of the gonadotrophs to the pattern of pulsatile GnRH release or is instead driven by a GnRH-independent mechanism. We have assessed the GnRH dependence of this singular FSH secretion by testing the ability of a potent GnRH antagonist (GnRHa: WY-45760) to block FSH and testicular responses to photostimulation. Photoinhibited hamsters were transferred from a short-day (6L:18D) to a long-day photoperiod (16L:8D). Hamsters received two daily injections of a GnRH antagonist or vehicle (VEH). After 0 (short day), 3, 5, 10, 30, or 40 days the hamsters were killed; plasma was assayed for FSH, LH, and testosterone (T), and testes weights were recorded. Testes were sectioned and analyzed for tubular development. In VEH-treated animals, testicular weights increased after photostimulation, reaching mean values of 514 mg by 30 days. Treatment with GnRHa resulted in a significant (p < 0.01) attenuation of testicular growth after 30 days of photostimulation (mean testes weight = 110.1 mg). In VEH-treated hamsters there was a rapid increase in FSH levels after photostimulation that became significant by 5 days and peaked at 10 days. In the GnRHa-treated group, however, these FSH increments were completely blocked at 5 days and significantly reduced at 10 days compared to the values in the corresponding VEH-treated groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Wolfe
A M
AM
Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208-3520, USA.
Turek
F W
FW
Levine
J E
JE
D000818:Animals; D006224:Cricetinae; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D006727:Hormone Antagonists / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D009929:Organ Size / Q000187:drug effects; D010052:Ovariectomy; D017111:Phodopus; D010775:Photic Stimulation; D011863:Radioimmunoassay; D013091:Spermatogenesis / Q000187:drug effects; D013737:Testis / Q000033:anatomy & histology / Q000187:drug effects / Q000254:growth & development*
D006727:Hormone Antagonists; D007987:Gonadotropin-Releasing Hormone; C042020:LHRH, acetyl-2-(2-naphthyl)-Ala(1)-4-F-Phe(2)-Trp(3)-Arg(6)-; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone