Alteration of platelet alpha 2-adrenoceptors in human hypertension.

We have previously demonstrated an alteration in cerebral and renal alpha 2-adrenoceptor densities in hypertensive rats. Since human platelets contain alpha 2-adrenoceptors, these receptors were measured in normotensive and hypertensive subjects using [3H]-rauwolscine to determine whether there was an alteration of alpha 2-adrenoceptors in human hypertension. In normotensive subjects, [3H]-rauwolscine bound to distinct high- and low-affinity alpha 2-adrenoceptor sites. In contrast, in platelets of hypertensive patients only the high-affinity alpha 2-adrenoceptor site was detectable. In addition, platelet alpha 2-adrenoceptor densities were higher in normotensive than in hypertensive subjects. This alteration, if present in other cells, could be important in the pathogenesis of hypertension.