Atrial natriuretic peptide modifies arterial blood pressure through nitricoxide pathway in rats

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, I mg/kg ) reverted the decrease in mean arterial pressure induced by ANP administra tion (5 mu g/kg bolus and 0.2 mu g.kg(-1). min(-1) infusion), and the injec tion 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 endotheli um and smooth muscle of aorta and arterioles of the small and large intesti ne. ANP increased aorta and arteriole endothelium staining after both in vi vo administration and in vitro tissue incubation. In both cases, L-NAME pre vented the ANP effect on NADPH-diaphorase activity. Tissues incubated with 8-bromoguanosine 3', 5'-cyclic monophosphate mimicked ANP action. In additi on, ANP administration increased urinary excretion of NO, end products. The se findings indicate that ANP increases NO synthesis capability and NO prod uction and suggest that the cGMP pathway may be involved. In conclusion, th e NO pathway could be an intercellular messenger in the ANP endothelium-dep endent vasorelaxation mechanism.