Intracellular sodium and blood pressure in Nigerians

In examining the relationship between erythrocyte sodium, potassium, and blood pressure in Nigerians, we measured the erythrocyte sodium and potassium in 25 hypertensive and 34 normotensive subjects. Of the normotensive subjects, 15 had positive family histories of hypertension and 19 did not. The hypertensive subjects were older (50.1 +/- 1.7 years) than the normotensive subjects (25.4 +/- 0.7 years) (mean +/- SEM; P < .001). The mean arterial pressure in hypertensive subjects was higher (108.8 +/- 2.3 mm Hg), as expected, compared with normotensive subjects (86.98 +/- 1.62 mm Hg) (P < .001). The mean duration of hypertension in hypertensive subjects was 5.60 +/- 0.75 years. Erythrocyte sodium was higher in hypertensive subjects (9.57 +/- 0.19 mmol/L) compared with normotensive subjects (7.96 +/- 0.19 mmol/L) (P < .001). Among normotensive subjects, erythrocyte sodium was higher in those with a positive family history of hypertension (8.59 +/- 0.31 mmol/L) compared to those without such a history (7.47 +/- 0.18 mmol/L), and this was also statistically significant (P = .027). Erythrocyte potassium levels were similar in the hypertensive subjects (83.51 +/- 0.71 mmol/L), in normotensive subjects (81.86 +/- 0.81 mmol/L), and in those without a family history of hypertension (80.20 +/- 0.51 mmol/L) (P = .675). We observed a significant (P < .001) positive correlation between erythrocyte sodium and systolic (r = 0.99) and diastolic (r = 0.39) blood pressures. Our findings support the hypothesis that erythrocyte sodium is closely related to blood pressure and its nonracial genetic determinants.