Published Online
on November 10, 2003

A more recent version of this article appeared on December 1, 2003

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Submitted on February 12, 2003
Revised on March 1, 2003

Determinants of Salt Sensitivity in Black and White Normotensive and Hypertensive Women

Jackson T. Wright Jr^*; Mahboob Rahman; Antonio Scarpa; Marjan Fatholahi; Valerie Griffin; Rachel Jean-Baptiste; Monir Islam; Moustafa Eissa; Suzanne White; and Janice G. Douglas

From the Departments of Medicine (J.T.W.Jr, M.R., S.W., J.G.D.), Physiology and Biophysics (A.S., M.F., J.G.D.), and Epidemiology and Biostatistics (M.R., R.J.-B., M.I.), Case Western Reserve University School of Medicine; the University Hospitals of Cleveland (J.T.W.Jr, V.G., M.E., J.G.D.); and the Louis Stokes Cleveland Veterans Affairs Medical Center (J.T.W.Jr), Cleveland, Ohio.

^* To whom correspondence should be addressed. E-mail: jxw20{at}po.cwru.edu.

Abstract--Salt sensitivity (SS) has been linked to human hypertension. We examined ethnic differences in the relation between SS; erythrocyte sodium (Na⁺_i), calcium (Ca²⁺_i), potassium (K⁺_i), and magnesium (Mg²⁺_i); and sodium pump activity in African-American (AA) and white women. In a crossover protocol, similar numbers of normotensive, hypertensive, AA, and white women were randomized to 7 days of a 20 meq/d and a >200 meq/d salt diet (n=199). After an overnight inpatient stay, group differences in supine blood pressure (BP), heart rate, erythrocyte cations, and sodium pump activity were measured. The prevalence of SS (53.5% vs 51%) and salt resistance (26.3% vs 30.0%) was similar in both races. Greater mean BP increase with salt loading was seen in AA vs white hypertensives but not between the normotensive women. In hypertensives, increase in mean arterial pressure was 12.6 vs 8.2 mm Hg in AAs vs whites, respectively (P<0.01), and for systolic BP, it was 23 vs 14.8 mm Hg (P<0.01). Higher Na⁺_i and Ca²⁺_i were noted in SS and salt-intermediate AA than in the corresponding white subjects. Na⁺_i, Ca²⁺_i, and the ratios of Na⁺_i to K⁺_i and of Ca²⁺_i to Mg²⁺_i were positively correlated with salt responsiveness in AA but not in white women. Sodium pump activity was similar between groups, although the change in maximal activity trended to vary inversely with SS in AA. In closely matched AA and white women, the prevalence of SS is similarly high in both races, although the magnitude of BP increase is greater in AA hypertensives. In AA but not in whites, SS is positively associated with Na⁺_i, Ca²⁺_i, and the ratios of Na⁺_i to K⁺_i and of Ca²⁺_i to Mg²⁺_i.

Key words: sodium • hypertension, sodium dependent • sodium, dietary • race • ethnicity • ions • sodium pump

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