A study of erythrocyte membrane cation transport adenosine triphosphatases in pregnancy-induced hypertension and of in vivo effects of diuretic treatment.

Plasma and erythrocyte Na+ and K+ and erythrocyte membrane (EM) Na+, K+ ATPase, Mg2+ ATPase and Ca2+, Mg2+ Atpase activities were studied in four groups of women -- non-pregnant, normal pregnant, with pregnancy edema (PE) and with pregnancy induced hypertension (PIH). The effect of diuretic therapy in PE and PIH was also evaluated. Plasma Na+ concentration was higher in PE and PIH. There was a significant reduction in (Na+ + K+) ratio between cell and plasma in these two groups. EM Na+, K+ ATPase was unaltered in PE and PIH. The Mg2+ ATPase was elevated by 44% in PE and by 100% in PIH subjects. There was a 50% reduction in Ca2+, Mg2+ ATPase activity in PE. Diuretic therapy had no effect either on electrolyte levels or on any of the EM ATPases. From these results it may be concluded that Na, K, ATPase -- which in kidney is a site of action for furosemide, a potent diuretic -- is unaffected in PE and PIH and, hence, treatment with diuretics -- is unaffected in PE and PIH and, hence, treatment with diuretics in such patients may be ineffective.