Differences in cell cation metabolism have been previously demonstrated between blacks and whites in the US. To investigate a potential racial/genetic basis for these differences we studied red cell sodium content (Nai) and platelet cytosolic calcium (Cai) in a group of US whites (n = 26), US blacks (n = 20) and West African blacks (n = 26) residing in Chicago, IL. Participants in all groups were primarily health professionals. The West Africans had lived in Africa until at least age 21 and subsequently resided in the US for an average of 19 months. Immunological markers were used to estimate European gene admixture among the US blacks. Red cell Nai was significantly lower in US whites (7.72 +/- 2.49 mEq/l cells) compared to both the US blacks and West African blacks (9.98 +/- 2.36 and 10.60 +/- 2.80, respectively; P less than 0.01) and Cai was higher in whites than among US blacks (P less than 0.05). No differences were noted in blood pressure (BP) levels among the three racial groups. A linear correlation existed between Nai and both systolic (SBP) and diastolic (DBP) (r = 0.378 and 0.339, respectively; P less than 0.01), which was strongest among the blacks, particularly the US blacks (SBP vs. Nai, r = 0.716, P less than 0.01). Approximately 20% European gene admixture was present among the US blacks. Based on these findings, it would appear that, compared to US whites, higher levels of RBC Nai are common to black persons native to the US and West Africa.(ABSTRACT TRUNCATED AT 250 WORDS)