Natriuretic response to atrial natriuretic factor enhanced by angiotensin II and vasopressin

The effect of angiotensin II (ANG II) and arginine vasopressin (AVP) on the natriuretic response to partially purified high molecular weight atrial natriuretic factor (ANF) was examined in anaesthetized rats. ANG II and AVP were infused continuously at equipressor doses. Rats receiving ANG II and AVP showed five- to sevenfold greater natriuretic responses to bolus injections of ANF than controls. A significantly smaller augmentation of the natriuretic response to ANF was produced by equipressor does of norepinephrine and epinephrine, suggesting that the potentiation by ANG II and AVP were not entirely due to increased mean arterial pressure (MAP). Decreased MAP in rats receiving infusions of saralasin and hydralazine did not diminish the natriuretic response to ANF. The results suggest that the ANG II and AVP augmentation of the ANF-induced natriuresis is mediated partly through increased MAP and partly by interacting with the renal action of ANF.