The effect of aging on ANP levels in the plasma, heart, and brain of rats.

Atrial natriuretic peptide (ANP) is a hormone important in the cardiovascular system via its regulatory roles in sodium and water excretion, and in vasodilatation. Aging represents a major risk factor in the development of hypertension, a perturbation which may activate compensatory mechanisms. The influence of aging on the ANP levels in plasma, atria, ventricles, hypothalamus, and brainstem was evaluated by comparing young (3 mo), middle-aged (12 mo), and old (24 mo) rats. Plasma and ventricular ANP levels increased with age, while ANP content in the atria as well as hypothalamus decreased significantly. PreproANP mRNA contents increased with age in the ventricle but not in the atrium. It is suggested that the increase in plasma ANP levels in old rats is due to the increase in ANP secretion from the atrium and the ventricle, partly as a result of an increase of release of ANP from hypothalamus.