Effect of antihypertensive treatment on the increased β2-adrenoceptor density in patients with essential hypertension

The effect of different antihypertensive drugs on the increased surface β2-adrenoceptor density in essential hypertension was evaluated to elucidate whether the possible effect of the treatment on these receptors was secondary to blood pressure decreases or a specific effect of the drugs. Thirty-nine untreated essential hypertensive patients and 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 verapamil SR (240 mg/day, n = 12), and were studied before and after 1 month of treatment. Plasma catecholamines were determined by a radioenzymatic assay. Surface β2-adrenoceptors were measured in intact lymphocytes by radioligand binding assay using the hydrophilic ligand [3H]-CGP12177. β2-adrenoceptor density was increased in hypertensive patients (P< .01). After treatment, mean blood pressure decreased similarly in the three groups, while plasma catecholamines showed no significant changes in any group. β2-adrenoceptor number decreased only in bisoprolol-treated patients (P< .05). Mean blood pressure decreases correlated with β2-adrenoceptor decrements only in bisoprolol-treated patients (r = 0.65, P< .05). β2adrenoceptor density correlated with plasma epinephrine levels in the control group (r = −0.50, P< .01), but not in hypertensive patients before treatment. This correlation was also observed in hypertensive patients treated with bisoprolol (r = −0.52, P< .05), but not in those treated with verapamil or enalapril. Our results suggest that bisoprolol treatment reduces the increased surface β2-adrenoceptor density and restores its regulation by epinephrine in essential hypertension. This effect seems to be specific to β-blockers, as these changes can be ascribed to neither blood pressure decreases nor to changes in plasma catecholamine levels.