Objective:Alterations in platelet α2-adrenoceptor and mononuclear leucocyte β2-adrenoceptor characteristics in primary hypertension have been extensively studied. The results of the reports have not been consistent, possibly because of the small number of subjects in most of the studies. We therefore studied the blood-cell adrenoceptor characteristics in a relatively large group of primary hypertensive and normotensive subjects.Design:Platelet α2-adrenoceptor characteristics were compared in 65 hypertensive and 51 normotensive subjects. Mononuclear leucocyte β2-adrenoceptor characteristics were compared in 72 hypertensives and 67 normotensives. Untreated hypertensive subjects were selected from the outpatient clinic and the normotensive controls were recruited by a newspaper announcement.Methods:Platelets and mononuclear leucocytes were isolated from blood samples obtained after at least 10 min supine rest. The α2- and β2-adrenoceptor characteristics were determined with [3H]-rauwolscine and [125I]-(—)cyanopindolol, respectively. Correlations between the adrenoceptor characteristics and clinical parameters of the subjects were studied.Results:No differences in α2- or β2-adrenoceptor densities were observed between the two groups. However, a significantly lower equilibrium dissociation constant for [3H]-rauwolscine was observed in the hypertensive group. The correlations between the adrenoceptor characteristics and clinical parameters were weak and mostly not statistically significant. The results were compared with the most relevant studies in the literature.Conclusions:From our study and the literature, we conclude that blood-cell adrenoceptor characteristics are unchanged in primary hypertension.