Pro-atrial natriuretic peptide (1–98): The circulating cardiodilatin in man

Abstract

The nature of plasma cardiodilatin, the amino-terminal product of the human pro-atrial natriuretic peptide, was investigated by two separate radioimmunoassays directed against the N-terminal and the putative C-terminal of the cardiodilatin molecule: ANP-[Asn 1-Lys 16] and ANP-[Lys 87-Arg 98], respectively. Serial dilutions of normal and cardiac failure plasma exhibited parallelism with the synthetic peptide standard curves in both assays. The concentrations of N- and C-terminal cardiodilatin-immunoreactivity equivalents (-IE) were significantly higher in cardiac failure patients. N-terminal-IE. 912±87, normal subjects 129±13 (mean±SEM); C-terminal-IE: 7979±1784, normal subjects 895±213 (both p<0.001). Although the concentrations determined by the two assays were not identical, significant correlations were found between them in both normal subjects ( r=.69 , p<0.001) and cardiac failure patients ( r=.72 , p<0.01). Characterisation by gel permeation and fast protein liquid chromatography demonstrated coelution of the N- and C-terminal cardiodilatin immunoreactivities in a single chromatographic peak. These results suggest that the circulating cardiodilatin in normal subjects and patients with cardiac failure contains the entire prohormone amino-terminal sequence ANP-[Asn 1-Arg 98].