The nitric oxide-cyclic GMP pathway is still undefined regarding regulation of the release of hepatic lipase (HTGL). It was found that L-arginine (Arg) stimulated the release of HTGL activity from rat hepatocytes in a time- and dose-dependent manner. L-Arg-stimulated release of HTGL activity was inhibited by N-monomethyl-L-Arg, which is a nitric oxide synthase inhibitor. L-Arg markedly increased the cyclic GMP content of hepatocytes in the presence of a cyclic GMP phosphodiesterase inhibitor, zaprinast. The release of the enzyme activity was also suppressed by methylene blue (a guanly cyclase inhibitor) and KT5823 (a cyclic GMP-dependent protein kinase inhibitor). These results suggest that the stimulation of nitric oxide synthesis by L-Arg increases the release of HTGL activity due to processes associated with the elevation of cyclic GMP level, probably through an activation of protein kinase.