Human and rat atrial natriuretic polypeptides and their precursors

A highly sensitive radio-immunoassay (RIA) to detect all the atrial natriuretic polypeptides (ANPs) isolated so far from human and rat (hANPs and rANPs) has been established by using an antiserum raised against alpha-hANP. The antiserum recognizes the sub-sequence flanked by two cysteine residues (positions 7 and 23) in alpha-hANP and cross-reacts with hANPs as well as rANPs. By using the RIA 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.