ALTERCATIONS IN BETA-ADRENOCEPTOR MECHANISMS IN THE AGING HEART - RELATIONSHIP WITH HEART-FAILURE

In chronic heart failure substantial and characteristic changes occur in the-function of the adrenergic nervous system. Studies in isolated left ventricular muscle and in single cardiomyocytes from experimental models of aging and, recently, from humans show an age-related reduce d contractile response to beta-adrenoceptor stimulation. ''beta-adreno ceptor desensitization'' is thought to be a general and common mechani sm to explain the age- and heart failure-related decrease in beta-adre noceptor response. The aim of this review is to compare alterations in beta-adrenoceptor mechanisms in physiological cardiovascular aging an d chronic heart failure. From an analysis of the overall data on the r ole of aging in beta-adrenoceptor regulation in human and animal heart s, it is possible to conclude that the reduced response to beta-agonis ts is common to all species and all cardiac tissues. Moreover, the age -related changes are limited to beta-adrenoceptor-G-protein (s)-adenyl yl cyclase system abnormalities, while the type and level of abnormali ties change with species and tissues. The modifications shown in the a ging heart are not very different from some observed in heart failure. In particular, both in aged and failing hearts we may see that the de crease in beta-adrenoceptor responsiveness is related to changes in G- protein function. (C) 1997, Editrice Kurtis.