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 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 mormmethyl arginine (l-NAME) on the release of prolactin from decidual tissue in vitro. Results: l-arginine, at 100 μmol/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 μmol/l) stimulated prolactin release. At 2 hours, the effects of l-arginine were reversed by l-NAME (100 μmol/l), which by itself was without effect. Incubation of tissue with l-NAME for 24 hours inhibited prolactin secretion (24 hours; P< .05, vs control); however, l-NAME 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.