C-type natriuretic peptide (CNP) is a newly identified peptide that is structurally related to atrial natri-uretic peptide (ANP). Although it has been suggested that CNP is released from the endothelium for the regulation of local vascular tone, no data are available concerning the vasodilatory response to CNP in humans.Methods and ResultsStrain-gauge plethysmography was used to determine the vasodilatory effects of intra-arterially infused CNP compared with the effects of ANP infusion in 11 patients with chronic heart failure (CHF) and 11 age-matched healthy controls. Graded doses of CNP and ANP (8, 16, 32, and 48 pmo.minm−1· dL−1tissue volume) were administered randomly into the nondominant brachial artery, and forearm blood flow (FBF) was measured. No significant changes in systemic blood pressure and heart rate were found during the study. Both the absolute and percent FBF responses to ANP relative to the baseline value were significantly lower in CHF patients than in healthy controls (P<.01), whereas the responses to CNP were similar. The calculated forearm spillover of cyclic GMP (cGMP) was significantly lower in CHF patients receiving the highest dose of ANP (P<.02), whereas changes in cGMP spillover after the equimolar dose of CNP were significantly higher (P<.02), despite the lesser potency of CNP.ConclusionsIn patients with CHF the peripheral vasodilatory effect of ANP is attenuated, but CNP-induced peripheral vasorelaxation is preserved, with CNP being less potent for equimolar doses.