Red blood cell sodium-lithium countertransport and cardiovascular risk factors in black and white college students

Whites with essential hypertension have high activity of cell membrane sodium-lithium (Na+-Li+) countertransport when compared with normotensives. To determine whether elevated Na+-Li+ countertransport is related to the twofold higher risk of hypertension in US blacks, maximal rates of red blood cell (RBC) Na+-Li+ countertransport were measured in 34 black and 21 white male college students. The race groups were similar in social and physical measurements. Mean Na+-Li+ countertransport activity (mmol Li/RBC per h) was significantly lower in blacks than in whites (0.214 +/- 0.083 versus 0.295 +/- 0.083, P less than 0.001). Countertransport activity was positively correlated with Type A behaviour among whites (r = 0.45, P = 0.039). Other within race correlations between Na+-Li+ countertransport activity and blood pressure and cardiovascular risk factors were generally positive though not significant in whites, whereas they were small or negative in blacks. If Na+-Li+ countertransport has a role in the aetiology of hypertension, it would appear to differ between blacks and whites.