Altered platelet alpha 2-adrenoceptors and adrenaline response in adolescents with borderline hypertension who have a family history of essential hypertension.

Abstract

We studied the relationship between a family history of essential hypertension and the characteristics of platelet alpha 2-adrenoceptors in male university students. Platelet membranes were prepared by the method of U'Prichard. Tritium-rauwolscine was used for the alpha 2-adrenoceptor binding assay. The maximum number of binding sites (Bmax) of platelet alpha 2-adrenoceptors was higher in borderline hypertensives with a family history of hypertension than in normotensives without it. However, no significant difference in the Bmax was found between the normotensives without and those with a family history. Dissociation constants (Kd) were not significantly different among the three groups. The plasma concentration of adrenaline after 30 min of standing was higher in the borderline hypertensives with a family history than in the normotensives, either with or without a family history. These results suggest that alterations in the alpha 2-adrenoceptor density or affinity for antagonists of platelets may not be linked to a positive family history of essential hypertension. However, an increased alpha 2-adrenoceptor density in platelets and an enhanced adrenaline response may be involved in blood pressure elevation in borderline hypertensives with a family history of hypertension.