Differences in Platelet Calcium Regulation Between African Americans and Caucasians

OBJECTIVE: To study differences in cytosolic free calcium regulation between African Americans and Caucasians, using platelets as a model for studying cellular physiology. DESIGN: Platelet calcium regulation in apparently healthy African American and Caucasian males was examined. METHODS: Using fura-2, calcium influx and cytosolic calcium extrusion were monitored after treatment with thapsigargin, an inhibitor of the Ca-ATPase in the dense tubular membrane system. RESULTS: Compared with Caucasians, platelets from African Americans demonstrated a higher calcium influx into the cytosol (from the external medium and dense tubular membrane system), as well as enhanced calcium extrusion from the cytosol. CONCLUSIONS: Such findings indicate that platelets from African Americans have increased intracellular calcium stores or increased cellular calcium turnover, or both. If these racial differences involve other cells, such as vascular smooth muscle cells, they could underlie the predisposition of African Americans to essential hypertension.