Renal and vascular effects of C-type and atrial natriuretic peptides in humans

C-type natriuretic peptide (CNP) may affect renal and vascular functions differently from atrial natriuretic peptide (ANP). The objective of this study was to compare the renal and vascular actions of CNP to those of ANP in normal men. CNP or ANP (0.005, 0.01, and 0.05 microg x kg(-1) x min(-1)) were given by infusion to eight healthy volunteers. CNP caused dose-dependent increases in natriuresis (U(Na)) and in the fractional excretion of sodium (FE(Na)) with no effect on diuresis (UV), renal plasma flow, and glomerular filtration rate (GFR). Fraction of filtration (FF) increased only with the 0.05 microg x kg(-1) x min(-1) CNP dose. ANP caused larger increases in U(Na), FE(Na), and FF than CNP and also increased UV at 0.01 and 0.05 microg x kg(-1) x min(-1) and GFR at 0.05 microg x kg(-1) x min(-1). Although the ANP and CNP infusions produced similar elevation in the respective peptides plasma levels, urinary and nephrogenous guanosine 3',5'-cyclic monophosphate increased less in response to CNP than to ANP. Blood pressure, forearm blood flow, plasma renin activity, and aldosterone remained unaffected during the peptides infusion. Plasma ANP increased slightly during CNP infusion. Our data indicate a higher threshold of renal response to CNP than to ANP. In contrast to ANP, CNP probably may not act as an endocrine factor in humans.