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 Mg⁺ 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 in such patients may be ineffective.