Measurement of circulating immunoreactive α-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 highly 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=1.004x-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 alpha-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.