Measurement of circulating immunoreactive alpha-atrial natriuretic peptide in human plasma: validation and clinical application.

Recent evidence suggests that plasma alpha-atrial natriuretic peptide (alpha-ANP) may serve as a useful biochemical marker of severe heart failure, as circulating levels become ighly elevated. In the present study, a specific radioimmunoassay (RIA) protocol was adapted and optimised for rapid quantitative measurement of circulating alpha-ANP levels in plasma taken from clinically normal subjects and heart transplant recipients with no evidence of heart failure or heart transplant rejection. The plasma concentration of immunoreactive alpha-ANP in heart transplant recipients (115 +/- 10 pg/ml, n = 14) was significantly higher (p < 0.01) than in normal subjects (14 +/- 5 pg/ml, n = 20). Comparison of circulating plasma immunoreactive alpha-ANP levels obtained by the adapted assay to levels obtained by a standard RIA protocol revealed a significant correlation (r = 0.998, y = 1.004 x -2.94, n = 40). The adapted assay is simple, precise, and with a shorter incubation time that would enable results to be available within one working day. These results show that circulating biological active a-ANP levels are elevated in healthy heart transplant recipients with no evidence of heart failure; thus extending previous reports concerning the elevation in circulating alpha-ANP levels from patients with a wide range of heart disorders. The adapted RIA protocol would facilitate rapid detection and quantification of alpha-ANP in experimental research and routine clinical investigations.