SODIUM-LITHIUM COUNTERTRANSPORT ACTIVITY IN NORMOTENSIVE OFFSPRING OFHYPERTENSIVE BLACK-AFRICANS

Objective: To assess sodium-lithium countertransport (SLC) activity an d erythrocyte sodium (ENa) levels in black (Nigerian) hypertensive (HT ) patients, normotensive (NT) offspring of hypertensive parents and no rmotensive offspring of normotensive parents, and to determine if incr eased SLC activity is related to a familiar predisposition to hyperten sion in black subjects as in Caucasians.Method: The study was done usi ng 60 Nigerian subjects of Edo ethnic origin in three groups of 20 eac h: (a) untreated new HT patients at the University Teaching Hospital, Benin City; (b)NT children of hypertensive parents (NTHT) traced home and matched for age, sex and body mass index (BMI) with (c) NT childre n of NT parents (NTNT). SLC activity was measured using a modified met hod of Canessa et al 1980 and ENa assessed by flame photometry. Result s: SLC was markedly higher in both HT patients and NTHT subjects than the NTNT subjects. The values were 0.351 +/- 0.011 vs 0.199 +/- 0.014 mmol Li/rbc (P < 0.0001) and 0.347 +/- 0.020 vs 0.199 +/- 0.014 mmol L i/rbc/hr (P < 0.0001), respectively. The values were not different bet ween the HT and the NTHT group (P > 0.05). ENa was higher in the HT gr oup than both NT groups which were similar. Values were 10.55 +/- 0.46 (HT) vs 7.78 +/- 0.62 (NTHT) (P < 0.0001) and 10.55 +/- 0.46 (HT) vs 8.62 +/- 0.47 mmol/L (P < 0.0001). There were no correlations between either SLC activity or ENa and any of the other measured variables suc h as age or BMT. Conclusions: SLC activity was elevated in normotensiv e children of hypertensive subjects to a similar degree as hypertensiv e patients and in a pattern reminiscent of that seen in Caucasians. SL C activity may thus be associated with a familiar predisposition to hy pertension in black subjects as in their Caucasian counterparts.