Alpha- and Beta-Adrenoceptors in Circulating Blood Cells of Essential Hypertensive Patients: Increased Receptor Density and Responsiveness

In 40 male patients with established essential hypertension (P diast greater than 95 mmHg) platelet alpha 2-adrenoceptor density (by 3H-yohimbine binding) and -responsiveness (by adrenaline-induced aggregation) as well as lymphocyte beta 2-adrenoceptor density (by (+/-)-125 iodocyanopindolol binding) and -responsiveness (by cyclic AMP responses to isoprenaline) were determined and compared with those in 40 male age-matched normotensives (P diast less than 90 mmHg). In essential hypertensive patients mean platelet alpha 2- and lymphocyte beta 2-adrenoceptor densities were significantly increased. When data from all 80 subjects were combined, significant positive correlations between mean arterial blood pressure and alpha 2- and beta 2-adrenoceptor densities, respectively, were found. The increases in alpha 2- and beta 2-adrenoceptor densities were accompanied by enhanced responsiveness to adrenergic stimulation: in platelets adrenaline-induced aggregation--via alpha 2-adrenoceptor stimulation--was exaggerated, and in lymphocytes isoprenaline produced significantly greater increases in the intracellular level of cyclic AMP. It is concluded that the increased density and responsiveness of alpha 2-and beta 2-adrenoceptors in circulating blood cells of essential hypertensive patients may reflect increased sympathetic activity, which might contribute to the elevation of blood pressure.