THE CHARACTERISTICS OF ERYTHROCYTE NA plus TRANSPORT-SYSTEMS IN NORMAL-PREGNANCY AND PREGNANCY-INDUCED HYPERTENSION

Objective: To assess the role Na plays in the pathogenesis of pregnancy-induced hypertension (PIH). Methods: We assessed Na and K content, the maximum number of ouabain binding sites, Na+-Li+ countertransport and Na+-K+ cotransport in erythrocytes from women with untreated PIH, normal pregnant women and healthy non-pregnant women. Results: In normal pregnancy, the Na content of erythrocytes decreased, accompanied by the activation of Na excretion systems. In women with PIH, the Na content of erythrocytes and the Na+-K+ cotransport activity significantly increased, whilst erythrocyte K content and the maximum number of ouabain binding sites significantly decreased, compared with observations in normal pregnancy. In both normal pregnancy and PIH, there were no differences in Na+-Li+ countertransport. Conclusions: These results suggest that the increase of erythrocyte Na content in women with PIH may be contributed to by a reduction in the number of ouabain binding sites, whilst Na+-K+ cotransport and Na+-Li+ countertransport may compensate for this effect in women with PIH.