Contrasting effects of a gonadotropin-releasing hormone agonist and antagonist on the secretion of free alpha subunit.
Gonadotropin-releasing hormone agonists and antagonists have initial divergent effects on the pituitary secretion of intact biologically active gonadotropins and long-term divergent effects on the secretion of free alpha-subunit. The antagonists appear to function as true competitive inhibitors, blocking the stimulatory effects of endogenous GnRH without evoking any known postreceptor activity. The agonists, in contrast, initially stimulate pituitary secretion and then incompletely desensitize the gonadotrope, resulting in suppression of intact gonadotropin, but not free alpha-subunit, secretion. The mechanisms by which GnRH-a produce this incomplete gonadotrope desensitization and facilitate limited postreceptor activity remain to be elucidated.
Fluker
M R
MR
Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco 94143-0132.
Monroe
S E
SE
Marshall
L A
LA
Jaffe
R B
RB
D000328:Adult; D004958:Estradiol / Q000097:blood; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D017274:Nafarelin / Q000494:pharmacology*; D009994:Osmolar Concentration
C043699:detirelix; D017274:Nafarelin; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone