Efficacy of piperine, an alkaloidal constituent of pepper on nitric oxide, antioxidants and lipid peroxidation markers in L-NAME induced hypertensive rats

A pharmacological inhibition of nitric oxide synthase (NOS) in rats produces vasoconstriction which causes hypertension. We have investigated that whether piperine ameliorates Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) - induced hypertension. Treatment of rats with L-NAME (40 mg/kg in drinking water for 4 weeks) caused a sustained decrease in the nitrite/nitrate concentrations (NOx) in plasma compared with control rats. Piperine restored the plasma NO metabolites concentration in L-NAME-treated hypertensive rats. Moreover, piperine significantly restored enzymatic (superoxide dismutase, catalase, glutathione peroxidase), non-enzymatic antioxidants (vitamin C, vitamin E and reduced glutathione) and decreased the levels of lipid peroxidation markers, compared to the L-NAME-treated group. Histopathological findings of piperine treated hypertensive rat heart confirmed the biochemical findings of this study. Taken together, these results suggest that L-NAME-induced hypertension is associated with decreased release of NO, an imbalance in antioxidant status and increased lipid peroxidation. Our results indicate that piperine attenuates hypertension on NO-deficient rats and that oxidative stress participates in the established phase of this type of hypertension.