Alterations 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 reduced contractile response to beta-adrenoceptor stimulation. "beta-adrenoceptor desensitization" is thought to be a general and common mechanism to explain the age- and heart failure-related decrease in beta-adrenoceptor response. The aim of this review is to compare alterations in beta-adrenoceptor mechanisms in physiological cardiovascular aging and chronic heart failure. From an analysis of the overall data on the role of aging in beta-adrenoceptor regulation in human and animal hearts, it is possible to conclude that the reduced response to beta-agonists is common to all species and all cardiac tissues. Moreover, the age-related changes are limited to beta-adrenoceptor-G-protein (s)-adenylyl cyclase system abnormalities, while the type and level of abnormalities change with species and tissues. The modifications shown in the aging heart are not very different from some observed in heart failure. In particular, both in aged and failing hearts we may see that the decrease in beta-adrenoceptor responsiveness is related to changes in G-protein function.