Action of C-type natriuretic peptide in isolated canine arteries and veins

C-type natriuretic peptide (CNP) is a hormone that shares structural homology to atrial natriuretic peptide (ANP); however, distinct receptors have been found for each in cultured aortic endothelial and smooth muscle cells. CNP in vivo reduces arterial pressure, atrial pressures, and cardiac output. These actions are consistent with a decrease in cardiac preload. Therefore, the current studies were designed to test the hypothesis that CNP is a vasodilator distinct from ANP. Rings of canine renal and saphenous arteries and renal, saphenous, and femoral veins with and without endothelium were suspended to measure isometric force in an organ chamber. CNP caused significant concentration-dependent relaxations in veins with and without endothelium contracted with phenylephrine (10(-6) log M). In marked contrast, ANP caused no significant relaxation in veins either with or without endothelium. In arterial rings, responses to the peptides were heterogeneous. ANP caused relaxation in renal but not saphenous arteries. CNP induced modest and comparable relaxation in rings of saphenous but not renal arteries with and without endothelium. These results demonstrate that: 1) CNP and not ANP is a relaxing factor of isolated peripheral canine veins, and 2) the responses of arteries to ANP and CNP are heterogeneous. These findings support a distinct biological role for CNP in the regulation of cardiovascular tone.