PLATELET ALPHA-ADRENOCEPTOR DENSITY IN PATIENTS WITH LEFT-VENTRICULARVOLUME OVERLOAD

We have evaluated the possibility that, in patients with left ventricu lar heart disease, the effects of aortic and mitral regurgitation on p latelet alpha(2)-adrenoceptors may depend on the origin and severity o f the overload. Receptor density and binding affinities were estimated by their specific binding to [H-3]-yohimbine. In blood donor controls (CON), the receptor density was 4.72 +/- 0.41 fmol/10(6) platelets (n = 31). In the volume overloaded patients (n = 35), the total density was elevated by 57% (p < 0.05) accompanied by a 69% (p < 0.05) increas e in plasma epinephrine. Compared with CON, patients with pure aortic regurgitation (AVR, n = 12) showed a 91% (p < 0.0001), pure mitral reg urgitation (MVR, n = 15) 43% (p < 0.05) and mixed mitral and aortic va lve regurgitation (MOL, n = 8) 23% increase in receptor density. Furth ermore, the elevation of the density in the aortic disease was signifi cantly greater (p < 0.05) than in the mixed overload group. There was a weak positive correlation between the increase in receptor density a nd the ejection fractions (r = 0.27), suggesting that the former may b e dependent on the severity of the volume overload. The results show t hat in left heart valvular disease, aortic regurgitation leads to a hi ghly significant increase in alpha-adrenoceptor density, while the eff ects of mitral valve disease exhibit borderline significance. These fi ndings probably point to the differences in the extent of influence of the origin and severity of the two forms of left ventricular volume o verload (LVO), as well as the ensuing hemodynamic changes on the cardi ac contractile apparatus.