Cardionatrin I - a novel heart peptide with potent diuretic and natriuretic properties.

Rat atrial muscle extracts are able to induce a powerful diuretic and natriuretic response. In the present work it was found that when rat atrial extracts are subjected to reverse phase-high pressure liquid chromatography, diuretic and natriuretic activities are recovered in four distinct chromatographic regions. From one of these chromatographic regions we purified to chemical homogeneity a peptide referred to as "Cardionatrin I" which has potent diuretic and natriuretic properties. Amino acid analysis showed that cardionatrin I has 49 residues, including one cystine, and a molecular weight of 5,499. Yield of cardionatrin I was 12-20 nmole per 1,000 atria. Injection of 0.5 nmole induced a characteristic diuretic and natriuretic response in the non-diuretic assay rat.