Role of the heart as an endocrine organ.

Cardiac atria and, under certain circumstances, also ventricles produce and secrete into the circulation atrial natriuretic factor (ANF). ANF exerts a significantly natriuretic, myorelaxant, renin-, aldosterone-, and vasopressin-inhibiting effect and acts as a neurotransmitter in the central and autonomous nervous systems. Expansion of the extracellular volume stimulates secretion of ANF which consequently contributes to renal excretion of sodium and water. The renal effect of ANF is apparently modulated by interaction with other mechanisms. ANF concentration in peripheral blood is the product of its secretion by the heart and degradation by peripheral tissues. In ascitic liver cirrhosis, the decreased splanchnic bed uptake may contribute to the increase in plasma ANF concentration observed. Insufficient production or secretion of ANF are not likely to be the primary etiopathogenic mechanism of arterial hypertension. In the course of development of hypertension, ANF is mobilized as a corrective-adaptive mechanism in an effort to normalize the raised BP, extracellular volume or circulating pressor agents. Through its production of ANF, the heart possess an important endocrine function markedly affecting pressure, electrolyte and volume homeostasis.