Atrial Natriuretic Factor

Abstract

A regulatory function of the cardiac atrium on the diuretic and natriuretic actions of the kidney has been known since the 1950s. The stimulation of these renal functions by increased atrial pressure had been considered to be mediated by a reflex mechanism. However, the discovery that rat atrial extracts (I), or more precisely, the content of the dense granules (2) in the atriomyocytes caused a potent and rapid natriuretic-diuretic response clearly demonstrated that a humoral factor (1) is mainly responsible for the atrial action on the kidney. A potent vasorelaxant activity was also found in the atrial extract (3-6). Persistent co-purification of the two activities (4) and subsequent synthesis (7, 8) demonstrated that the two activities resided in the same peptide substance. Subsequent development of a specific radioimmunoassay (9, 10) and immunohistochemical localization (11,12) firmly established that the atrium is the major storage organ of ANF' which is secreted and circulates in the blood (10, 13). These findings established ANF as a circulating hormone, and the cardiac atrium can be regarded as an endocrine organ. Furthermore, like many other peptide hormones, ANF was also demonstrated in the brain (10).