COMPARISON OF THE EFFECT OF LEFT-VENTRICULAR VOLUME AND PRESSURE-OVERLOAD ON BETA-ADRENOCEPTOR DENSITY IN LEFT-HEART VALVULAR DISEASE

The sympathetic responses in left heart valvular disease may depend on the ventricular load conditions. We proposed to evaluate this possibi lity by comparing the effects of left ventricular pressure (LVP) and v olume (LVV) overload on beta-adrenoceptor density and ligand binding a ffinity in lymphocytes and in the four myocardial chambers in rheumati c heart valvular patients. Receptor activity was determined by radioli gand binding using [I-125]iodocyanopindolol. In the lymphocytes (n = 4 5), the beta-adrenoceptor density was reduced by 88% (P < 0.001) in LV P patients (n = 15) and 79% (P < 0.001) in LVV patients (n = 30) compa red with 23 controls. In the myocardium, the receptor density of the L VP (n = 12) was attenuated by 55% (P < 0.05) in the left ventricle, 42 % in the right ventricle, 13% in the left atrium, and 37% in the right atrium, while in LVV patients (n = 22) it decreased by 73% (P < 0.01) in the left ventricle, 62% (P < 0.05) in the right ventricle, 30% in the left atrium, and 34% in the right atrium compared with 15 controls . Thus, the reduction in density was greatest in lymphocytes and least in the atria in both groups. The decrease in ventricular density of t he LVV group was similar to the reduction in the lymphocytes and two-f old higher than in the atrial density. These alterations were signific antly greater for the LVV than for the LVP group. The K-d for the myoc ardial receptor binding to [I-125]iodocyanopindolol was not significan tly influenced in either group, but was lower in the lymphocytes. Thes e findings suggest that in patients with left heart valvular disease, there is a significant attenuation in both peripheral and myocardial b eta-adrenoceptor density. The decrease in receptor density is signific antly greater in the left ventricular volume overload than in the left ventricular pressure overload patients.