The effects of L-arginine on the release of prolactin from decidual explants in vitro

OBJECTIVE: Our aim was to elucidate a role for the L-arginine-nitric oxide- cyclic guanosine monophosphate pathway in the control of decidual prolactin release in vitro. STUDY DESIGN: In decidua obtained from normal vaginal deliveries, we examin ed the effects of L-arginine; a stable analog of cyclic guanosine monophosp hate, 8-bromo-cyclic guanosine monophosphate; and two nitric oxide synthase inhibitors, L-nitro arginine methyl ester (L-NAME) and L-nitro monomethyl arginine (L-NMMA) on the release of prolactin from decidual tissue in vitro . RESULTS: L-arginine, at 100 mu mol/L, produced an increase in medium prolac tin concentration after a 2-hour exposure; however, its inactive isomer, D- arginine, at the same concentration; bid not. The increase in prolactin rel ease initiated by L-arginine was sustained after a 24-hour incubation. In a ddition, 8-bromo-cyclic guanosine monophosphate (10 mu mol/L) stimulated pr olactin release. At 2 hours, the effects of L-arginine were reversed by L-N AME (100 mu mol/L), which by itself was without effect. Incubation of tissu e with L-NAME for 24 hours inhibited prolactin secretion (24 hours; P<.05, vs control); however, L-NMMA was without effect. CONCLUSIONS: These results suggest that the L-arginine-nitric oxide-cyclic guanosine monophosphate pathway is involved in the regulation of prolactin secretion by decidual tissue.