Infusion of iso-rANP(1–45) or (17–45) increases plasma immunoreactive ANP and lowers plasma renin activity and aldosterone

Abstract

We have reported that a second rat atrial natriuretic peptide, iso-rANP(1–45), as well as the putative ANP homologue, iso-rANP(17–45), elicited circulatory and renal responses in the rat similar to those found after administration of ANP. Iso-rANP also interacted with ANP to potentiate the observed biological activity in the rat. In the present studies in awake dogs, intravenous infusion of low doses (6.3–50 pmol∙kg−1∙min−1) of iso-rANP(1–45) and iso-rANP(17–45) increased plasma immunoreactive ANP and suppressed plasma renin activity (PRA) and aldosterone. Iso-rANP, like ring-deleted analogues of ANP, may have displaced ANP from ANP clearance receptors to increase plasma ANP concentration, since factors influencing myocardial ANP release were not changed. The effect of iso-rANP(1–45) and (17–45) in lowering PRA and plasma aldosterone may therefore have been indirect, via ANP stimulation of active guanylate cyclase-linked ANP receptors. However, an additional direct effect of iso-rANP on an active receptor cannot be excluded.Key words: clearance and active ANP receptors, arginine vasopressin, water and electrolyte balance, circulatory hemodynamics.