The relaxant effects of atrial natriuretic factor on vascular smooth muscle

Extracts prepared from rat atria, which cause natriuresis and diuresis when injected into bioassay rats, relax aortic smooth muscle preparations. A family of atrial peptides has been isolated, purified and synthesized which elicit similar biological responses as the atrial extracts. The in vitro vasodilator profile of synthetic atrial natriuretic factor (sANF) exhibits many similarities to sodium nitroprusside including inhibition of agonist-induced but not high-K+-induced contractions, relaxation independent of the vascular endothelium and elevation of cyclic GMP in aortic smooth muscle coincident with relaxation. Aortic rings remain relaxed in the presence of sANF but can be recontracted following a sufficient washout period. sANF causes a significant activation of the particulate (but not soluble) form of guanylate cyclase which is seemingly consistent with the presence of high affinity receptors for sANF in plasma membranes prepared from aortic tissue. Both species and regional vascular differences exist for the vasodilator activity of the synthetic atrial peptides.