Molecular forms of atrial natriuretic polypeptides in mammalian tissues and plasma

A highly sensitive radioimmunoassay detecting for all the atrial natriuretic polypeptides isolated so far from human and rat (hANPs and rANPs) has been established by using an antiserum raised against alpha-hANP, since the antiserum recognizes the subsequence flanked by two cysteine residues (positions 7 and 23) in alpha-hANP and crossreacts with human as well as rat ANPs. By using the radioimmunoassay combined with gel chromatography or high performance liquid chromatography, it was revealed that ANP immunoreactivity in human atria is composed of alpha-(28 residues), beta-(56 residues: alpha-hANP dimer) and gamma-hANP(126 residues) in various ratios. In rat, porcine and bovine atrial tissues, however, gamma-rANP(126 residues) was found to be a major component. In contrast with atrial ANP, plasma ANP was found to be predominantly alpha-form in rat.