Effect of a purified atrial natriuretic factor on rat and rabbit vascular strips and vascular beds

Rat atrium cardiocytes contain a powerful natriuretic and diuretic peptide that has been localized in the specific granules. This atrial natriuretic factor (ANF) produced a potent, dose-dependent relaxant effect on rabbit and rat arterial strips previously made to contract by application of either norepinephrine (NE) or angiotensin II. The effect was not seen if KCl was used as contractile agent or under any conditions with rabbit mesenteric strips. After the application of ANF the vascular strips were refractory to subsequent stimulation by either NE or angiotensin II. The infusion of ANF into a high-resistance isolated perfused rat kidney produced a rapid decrease (33 +/- 5 mmHg) in perfusion pressure that lasted for 18 +/- 3 min. This effect was not seen in the isolated rat mesenteric arterial preparation, even when the perfusion pressure was raised by the infusion of NE. These effects of ANF on vascular smooth muscle are not mediated by prostaglandins, by alpha- and beta-adrenergic and muscarinic receptors, or by an impairment of Ca2+ influx, but they are mimicked by sodium nitroprusside. A low- and a high-molecular-weight ANF produced the same effects. The existence of specific receptive sites for these peptides is suggested.