Sex and race differences in sodium-lithium countertransport and red cell sodium concentration.

A total of 417 individuals from all four major sex-race groups were examined for the rate of sodium flux via the countertransport pathway and the sodium concentration within red cells. The age span was from early adolescence to retirement. Males of both races had sizable higher countertransport rates than did women (p less than 0.01), and a slight increase in sodium concentration (p greater than 0.05). Contrariwise, while whites or both sexes had higher countertransport than their black counterparts, sodium concentration was higher in blacks than whites (p less than 0.01). This pattern is not consistent with a direct relationship between both countertransport or sodium concentration and blood pressure which applies across both racial groups. Sex-race differences must be taken into account in any group comparisons of these variables.