Li efflux in erythrocytes of pregnant women: comparison of rates and temperature dependence for detection of hypertension.

Two determinants of lithium efflux in erythrocytes were compared, in relation to pregnancy: (a) efflux rates at 37 degrees C; (b) efflux temperature dependence, expressed by the 'break' of Arrhenius plots. Eighteen women were studied both at term and after delivery. While efflux rates were changed markedly, from 0.87 +/- 0.07 to 0.56 +/- 0.05 mmol/ (IRBC h) at term and post-partum, respectively, the characteristic break temperature of each woman remained essentially constant during and after pregnancy. The property of temperature dependence is more suitable than efflux rates for differentiation of hypertension during pregnancy.