MEDIATION BY NITRIC-OXIDE OF LH-RH-STIMULATED GONADOTROPIN SECRETIONSIN HUMAN-SUBJECTS

In order to establish whether nitric-oxide (NO) participates in the re gulation of gonadotropin secretion in humans, seven normal men were tr eated with a placebo (normal saline) or the NO synthase inhibitor L-NA ME, given at doses (40 mu g/kg injected plus 50 mu g/kg infused i.v.) previously found to be unable to change blood pressure. Experiments we re carried out either in basal conditions or during stimulation of gon adotropin secretion with an intravenous injection of 100 mu g LH-RH. T he administration of L-NAME was unable to change the basal secretion o f FSH and LH. In contrast, L-NAME significantly reduced both FSH and L H increments induced by LH-RH. These data fail to provide evidence of NO involvement in regulation of basal gonadotropin secretion. In contr ast, the inhibitory effect of L-NAME On LHRH-induced LH and FSH secret ion suggests the modulation by NO of the gonadotropin releasing action of LH-RH.