IMPAIRED REGULATION OF LYMPHOCYTE BETA(2) -ADRENOCEPTORS IN A SUBSET OF PATIENTS WITH ESSENTIAL-HYPERTENSION

The sympathetic nervous system has been implicated in the pathogenesis of essential hypertension. However, plasma catecholamine levels have been reported to be within the normal range in the majority of patient s with essential hypertension, although an increased adrenergic respon se in target tissues has not been ruled out. The aim of this study was to evaluate the state of beta-adrenoceptors, which are the effecters of the sympathetic nervous system in target tissues, in essential hype rtension. We studied 52 non-treated hypertensive patients and 28 normo tensive controls of similar age and sex. beta(2)-adrenoceptors were me asured in intact lymphocytes, using the hydrophilic ligand [H-3]GCP-12 177. Hypertensive patients showed values of mean blood pressure (p < 0 .01), heart rate (p < 0.01) and body mass index (p < 0.05) higher than normotensive controls, although there were no significant differences in plasma catecholamine levels between both groups. A positive relati onship was found between beta(2)-adrenergic receptors and mean blood p ressure when both hypertensive patients and control subjetcs were cons idered together (r = 0.40, p < 0.01). Hypertensive patients showed a m ean beta-adrenoceptor density higher than normotensive controls (1,881 +/- 567 vs 1,344 +/- 207 receptors/lynphocyte, p < 0.01), but there w as a considerable overlap. Hypertensive patients were subclassified in to two groups: Group I: hypertensive patients with a normal beta-adren oceptor density (< 7,100, n = 26), and Group II: hypertensive patients with an increased receptor density (> 1,100, n = 26). There were no d ifferences with respect to age, sex, body mass index, mean blood press ure, heart rate, plasma catecholamine levels or receptor affinity betw een the two groups of patients. In normotensive subjects there was an inverse relationship between plasma epinephrine levels and beta-adreno ceptor density (r = - 0.51, p < 0.01). A similar finding was observed in the hypertensive patients from Group I (r = - 0.44, p < 0.05), wher eas hypertensive patients from Group II showed no such correlation. Ou r results suggest that there is an important subset of essential hyper tensive patients who have an impaired beta(2)-adrenoceptor regulation, which is demonstrated by an increased beta(2)-adrenoceptor density an d by an alteration in the physiological regulation by its endogenous a gonist.