Racial Differences in Cell Membrane ATPases and Cellular Cation Content in Urban South African Normotensive and Hypertensive Subjects

Platelet and erythrocyte membrane Na+,K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase activities and platelet, erythrocyte and serum magnesium, calcium, sodium and potassium concentrations were determined in black (n = 52) and white (n = 24) essential hypertensive patients from the city of Johannesburg in South Africa. The hypertensive groups were matched for age and body mass with black (n = 52) and white (n = 26) normotensive controls. In the black group, platelet and erythrocyte membrane ATPase activities were significantly depressed in the hypertensive subjects. In the white group, there were no significant differences for any of the ATPases studied between the normotensive and hypertensive subjects. Platelet sodium and calcium were significantly increased and serum magnesium, serum potassium, platelet magnesium and erythrocyte magnesium significantly decreased in the black hypertensive group compared to the black normotensive group. In the white hypertensive patients, platelet sodium and calcium were significantly raised and platelet magnesium significantly decreased compared to the normotensive controls. In blacks, platelet magnesium and ATPase activity were negatively correlated with mean arterial pressure. Unlike whites, black hypertensives have widespread magnesium changes with associated cell membrane ATPase depression and cytosolic sodium and calcium accumulation. These results suggest possible racial differences in cellular cation regulation in essential hypertension.