| Abstract: | 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 examined the effects of L -arginine; a stable analog of cyclic guanosine monophosphate, 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 micromol/L, produced an increase in medium prolactin concentration after a 2-hour exposure; however, its inactive isomer, D -arginine, at the same concentration, did not. The increase in prolactin release initiated by L -arginine was sustained after a 24-hour incubation. In addition, 8-bromo-cyclic guanosine monophosphate (10 micromol/L) stimulated prolactin release. At 2 hours, the effects of L -arginine were reversed by L -NAME (100 micromol/L), which by itself was without effect. Incubation of tissue with L -NAME for 24 hours inhibited prolactin secretion (24 hours; P less than .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. |
