Atrial natriuretic peptide in man.

The heart is the major source of atrial natriuretic peptides (ANP). A propeptide is stored in atrial myocytes. In normal humans, atrial distension secondary to volume overload and/or increased atrial pressures are thought to stimulate the secretion of biologically active alpha-ANP (ANF-[99-126], 28 amino residues) into the circulation. Plasma immunoreactive ANP (irANP) rises in response to acute sodium-volume loading, the central shift of volume produced by lying down or by immersion, acute increases in blood pressure (BP), dynamic exercise, or the administration of glucocorticoids or mineralocorticoids. Plasma irANP also rises with aging. Synthetic alpha-ANP infused acutely i.v. can lower BP, reduce plasma volume by an extravascular shift, cause baroreflex-mediated sympathetic activation, directly inhibit adrenal steroidogenesis and lower plasma aldosterone and cortisol, directly inhibit renal renin release, elevate plasma insulin; diuresis, free water clearance and natriuresis increase already in response to low alpha-ANP doses that raise plasma irANP within the physiological-pathological range. It follows that in addition to direct influences on cardiovascular and renal function, the ANP system may comprise a cardio-adrenal feedback mechanism and perhaps also modulate insulin and the release of ADH. The major although yet unproven physiological role of the ANP system may be the protection of the heart against volume and/or pressure overload. The pathophysiological, diagnostic and therapeutic aspects of elevated plasma irANP values, ANP measurements, or administration of synthetic ANP, respectively, in various diseases are currently under intense study and of great potential interest.