Vasodilating actions of calcitonin gene-related peptide in normal man: comparison with atrial natriuretic peptide

To compare the vasodilator effect of calcitonin gene-related peptide (CGRP) with that of atrial natriuretic peptide (ANP), forearm blood flow (FBF) was measured by strain-gauge plethysmography during the continuous infusion of different doses of the peptides dissolved in 5% dextrose into the brachial artery in healthy subjects. Either CGRP or ANP increased FBF in a dose-dependent fashion. Although 100 ng/ml CGRP increased FBF from 3.27 +/- 0.41 to 10.70 +/- 1.77 ml/100 ml/min, the same dose of ANP increased FBF from 2.40 +/- 0.38 to 5.39 +/- 0.22 ml/100 ml/min, which was significantly lower than the increase in CGRP (p less than 0.01): Plasma concentration of peptides (on a molar basis) was positively correlated with FBF in CGRP (r = 0.820, p less than 0.01) or ANP (r = 0.722, p less than 0.01). However, the slope of the regression line between plasma level and FBF was significantly higher (p less than 0.01) in CGRP (12.88 +/- 0.99) than in ANP (2.10 +/- 0.27). Thus the vasodilator effect of CGRP was more potent than that of ANP. The present findings are compatible with functional involvement of CGRP in the regulation of forearm circulation.