ABSENCE OF BLACK-WHITE DIFFERENCES IN SODIUM AND CALCIUM IN PLATELETS

Consistent differences in sodium transport in red blood cells are obse rved in blacks compared to whites and have been the basis for speculat ion regarding physiologic differences in the vascular bed as well. The theoretical link between these metabolic markers and the risk of hype rtension generally assumes a secondary effect on calcium. Calcium meta bolism in red cells is difficult to study, however, so this propositio n has never been tested directly. Given the growing importance of plat elets in this area of research, and the availability of sensitive labo ratory methods, we carried out a systematic examination of calcium and sodium homeostasis in this cell line among black and white normotensi ve subjects. No differences were noted in resting cytosolic calcium, m obilizable stores, agonist-induced response, or sodium-calcium exchang e. In addition, resting sodium was not different between groups, nor w as the increase in sodium induced by ouabain. A correlation of 0.3 was observed between blood pressure and both resting and stimulated cytos olic calcium (P < .05). Red cells may be atypical for studies of calci um and sodium homeostasis, and their relevance for interethnic studies of causal pathways in hypertension should be reconsidered.