Atrial Natriuretic Peptide Modifies Arterial Blood Pressure Through Nitric Oxide Pathway in Rats

Abstract—The aim of the present study was to determine the relationship between the hypotensive effect of the atrial natriuretic peptide (ANP) and the nitric oxide (NO) pathway. NG-nitro-L-arginine methyl ester bolus (L-NAME, 1 mg/kg) reverted the decrease in mean arterial pressure induced by ANP administration (5 mg/kg bolus and 0.2 mg z kg21 z min21 infusion), and the injection of L-NAME before peptide administration suppressed the ANP hypotensive response. To confirm these findings, a histochemical reaction was used to determine NADPH-diaphorase activity (a NO synthase marker) in the endothelium and smooth muscle of aorta and arterioles of the small and large intestine. ANP increased aorta and arteriole endothelium staining after both in vivo administration and in vitro tissue incubation. In both cases, L-NAME prevented the ANP effect on NADPH-diaphorase activity. Tissues incubated with 8-bromoguanosine 39, 59-cyclic monophosphate mimicked ANP action. In addition, ANP administration increased urinary excretion of NOx end products. These findings indicate that ANP increases NO synthesis capability and NO production and suggest that the cGMP pathway may be involved. In conclusion, the NO pathway could be an intercellular messenger in the ANP endothelium-dependent vasorelaxation mechanism. (Hypertension. 2000;35:1119-1123.) Key Words: natriuretic peptides n nitric oxide n arterial pressure n NADPH diaphorase n cyclic GMP n vasodilation Atrial natriuretic peptide (ANP) and nitric oxide (NO), afree radical in the form of a highly diffusible gas, are vasoactive substances that induce hypotension through thei