[Atrial natriuretic factor: a "physiological diuretic"]

Abstract

Investigators are studying for hardly more than 10 years the special role of the atrial natriuretic peptide, "the physiological diuretic", in maintaining of the volume homeostasis. The ANF is synthesized in the atrial granules and also in extra-atrial organs; there are more members of this peptide family: the brain natriuretic peptide, the C-type natriuretic peptide and the urodilatin. The release of ANF is stimulated mainly by atrial wall distension, but some other mechanism may regulate its secretion too. It has regulatory properties on the cardiovascular, renal and endocrine systems. The most important vascular and renal effects of the hormone are as follows: vasodilatation, decrease in blood pressure, increase in glomerular filtration rate, renal blood flow, and filtration fraction, inhibition of sodium and water reabsorption in the proximal and distal renal tubules (natriuresis and diuresis), and decrease in concentrating ability. ANF is the counterregulatory hormone of the renin-angiotensin-aldosterone system. Its other endocrine interactions are complex, mutual stimulation and inhibition between ANF and vasopressin takes place either. The serum level is often elevated in edematous disorders, but there may be tubular resistance to the hormone's action. The therapeutical importance of this "physiologic diuretic" in volume retaining disorders has been proposed, but it needs further studies to establish the clinical therapeutical value of the hormone.