Atrial natriuretic peptide effect on NADPH-diaphorase in rat intestinal tract

Histochemical reaction of NADPH-diaphorase (NOS-NADPH-d) was used to identi fy NO synthesis. A 30-min 0.1 mu g/kg/min ANP infusion led to about a 10% a nd 35% increase in small and large intestine enterocytes stain respectively . This increase was abolished by a bolus of 1 mg/kg L-NAME before ANP infus ion in small intestine, and partially abolished it in colon. Incubation of small and large intestine with 0.5 mu M ANP increased stain at about 20%. I n both tissues the preincubation with 0.1 mM L-NAME abolished the ANP effec t. Incubation with 0.1 mM 8-Br-cGMP enhanced staining about 70% and 30% in small and large intestine respectively. Our results show that ANP enhances NOS-NADPH-d activity, suggesting that ANP stimulates NO synthase in enteroc ytes by L-arginine-NO pathway. 8-Br-cGMP mimicked the effect of ANP describ ed above. Therefore, the guanylate cyclase-coupled natriuretic receptors, N PR-A and NPR-B, probably mediate this ANP effect. (C) 1999 Elsevier Science Inc. All rights reserved.