The characteristics of erythrocyte Na+ 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.