[Changes in myocardial beta adrenergic receptors in left ventricular hypertrophy caused by barometric and volumetric...

While most prior studies examined late stages of heart failure, we determined initial changes of beta-adrenergic receptors (beta-AR) during left ventricular chronic volume and pressure overload. We investigated right auricular (RA) and left ventricular (LV) beta-AR density (Bmax, fmoles/mg protein) and beta 1-AR percentage in two groups of patients undergoing valve replacement without LV systolic dysfunction (LV ejection fraction > or = 60%), with normal plasma catecholamine levels and echocardiography LV hypertrophy. These results were compared with the values of a control group, composed by 8 patients with mitral stenosis and 5 cardiac transplant donors, and the values of 5 patients undergoing heart transplantation because of end-stage idiopathic dilated cardiomyopathy. These results show that, before alteration of LV systolic function occurs, left ventricular chronic overload induces a selective down-regulation of LV beta 1-AR compensated by an increase in beta 2-AR. These variations may be due to LV hypertrophy induced by volume or pressure overload.