Radioimmunoassay for atrial natriuretic peptide: method and results in normal subjects and patients with various diseases.

A sensitive and specific radioimmunoassay for alpha-human atrial natriuretic polypeptide (alpha-hANP) was developed to determine its plasma level. Anti-alpha-hANP rabbit serum was specific for the N-terminus and ring structure of alpha-hANP, and showed no appreciable cross-reactions with other neuropeptides. The lowest level of alpha-hANP detectable by this radioimmunoassay was 4 pg per tube. The intra- and inter-assay coefficients of variation were 4.6-11.4% and 7.9-11.8%, respectively, and the recovery rates at 4 concentrations were 62.6-74.0%. The fasting plasma alpha-hANP concentration in normal subjects were 19.3 +/- 1.0 ng/l (mean +/- SE; n = 54), and there was no sex difference. The plasma alpha-hANP level in normal subjects fell significantly during water deprivation and increased significantly on infusion of hypertonic saline. The mean plasma levels of alpha-hANP were higher than normal in patients with essential hypertension, liver cirrhosis, congestive heart failure and chronic renal failure. Our results indicate that this radioimmunoassay is suitable for determining the alpha-hANP concentration in human plasma and can assess changes in pathological and physiological states.