EFFECT OF ANTIHYPERTENSIVE TREATMENT ON THE INCREASED BETA(2)-ADRENOCEPTOR DENSITY IN PATIENTS WITH ESSENTIAL-HYPERTENSION

The effect of different antihypertensive drugs on the increased surfac e beta(2)-adrenoceptor density in essential hypertension was evaluated to elucidate whether the possible effect of the treatment on these re ceptors was secondary to blood pressure decreases or a specific effect of the drugs. Thirty-nine untreated essential hypertensive patients a nd 28 normotensive control subjects were studied in basal conditions. Hypertensive patients were randomly assigned to three treatment groups : bisoprolol (10 mg/day, n = 15), enalapril (20 mg/day, n = 12), and v erapamil SR (240 mg/day, n = 12), and were studied before and after 1 month of treatment. Plasma catecholamines were determined by a radioen zymatic assay. Surface beta(2)-adrenoceptors were measured in intact l ymphocytes by radioligand binding assay using the hydrophilic ligand [ H-3]-CGP12177. beta(2)-adrenoceptor density was increased in hypertens ive patients (P < .01). After treatment, mean blood pressure decreased similarly in the three groups, while plasma catecholamines showed no significant changes in any group. beta(2)-adrenoceptor number decrease d only in bisoprolol-treated patients (P < .05). Mean blood pressure d ecreases correlated with beta(2)-adrenoceptor decrements only in bisop rolol-treated patients (r = 0.65, P < .05). beta(2)-adrenoceptor densi ty correlated with plasma epinephrine levels in the control group (r = -0.50, P < .01), but not in hypertensive patients before treatment. T his correlation was also observed in hypertensive patients treated wit h bisoprolol (r -0.52, P < .05), but not in those treated with verapam il or enalapril. Our results suggest that bisoprolol treatment reduces the increased surface beta(2)-adrenoceptor density and restores its r egulation by epinephrine in essential hypertension. This effect seems to be specific to beta-blockers, as these changes can be ascribed to n either blood pressure decreases nor to changes in plasma catecholamine levels.