Immunoreactive IV-terminal pro-atrial natriuretic peptide in human plasma: plasma levels and comparisons with a-human atrial natriuretic peptide in normal subjects, patients with essential hypertension, cardiac transplant and chronic renal failure

1. Plasma levels of immunoreactive N-terminal proatrial natriuretic peptide (N-terminal ANP) have been measured in 25 normal subjects, 29 patients with essential hypertension, six cardiac transplant recipients, seven patients with dialysis-independent chronic renal failure and 1 1 patients with haemodialysis-dependent chronic renal failure. Plasma was extracted on Sep-Pak cartridges and N-terminal ANP immunoreactivity was measured using an antibody directed against pro-ANP (1-30). 2. Plasma levels of N-terminal ANP (means f SEM) were 235.3f 19.2 pg/ml in normal subjects and were significantly raised in patients with essential hypertension (363.6 k 36.3 pg/ml), in cardiac transplant recipients (1240.0 k 196.2 pg/ml), in patients with chronic renal failure not requiring dialysis ( 1636.6 k 488.4 pg/ml) and patients with chronic renal failure on maintenance haemodialysis (10 336.1 f 2043.7 pg/ml). 3. There were positive and significant correlations between the plasma levels of N-terminal ANP and ahuman ANP (a-hANP) with individual correlation coefficients of 0.68 within the normal subjects, 0.47 in patients with essential hypertension, 0.78 in patients with dialysis-independent chronic renal failure and 0.68 in patients with haemodialysis-dependent chronic renal failure ( P < 0.05 in every case). 4. Gel filtration behaviour on Sephadex G-50 of the immunoreactive N-terminal ANP from Sep-Pak extracts of plasma from normal subjects or patients was consistent with a single peak having an elution volume corresponding to that of human pro-ANP (1-67) standard.