B-type natriuretic peptide isolated from frog cardiac ventricles.

A new natriuretic peptide with 27 amino acid residues has been isolated from cardiac ventricles of the bullfrog, Rana catesbeiana. Since this ventricular peptide had high sequence identity to B-type (brain) natriuretic peptide (BNP), especially to chicken BNP (74%), we named it bullfrog BNP. Thus, semi-aquatic amphibians have tetrapod-type BNP, but do not seem to have fish-type ventricular natriuretic peptide (VNP) in their ventricles. Compared with other known BNPs, the C-terminus of bullfrog BNP was elongated by two amino acid residues and was not amidated. Bullfrog BNP dose-dependently decreased arterial blood pressure in the bullfrog with a potency twofold greater than that of human ANP. Bullfrog BNP also exhibited vasodepressor, natriuretic and diuretic activities in the rat, but it was 1/3, 1/7, and 1/17 as potent as human ANP in this mammalian species.