Cellular Sodium Transport in Severe Preeclampsia and Chronic Hypertension During Pregnancy

Background: There are contrasting reports on cation transport during hypertensive pregnancies, with either increased or decreased sodium-potassium pump function compared to normotensive pregnancies. Methods: Intraerythrocyte sodium and potassium content as well as transmembrane sodium transport were investigated in the third trimester in normotensive (n = 11), chronic hypertensive (n = 16), and severe preeclamptic (n = 6) pregnancies. Results: There was a significant decrease in intraerythrocyte potassium content and in sodium efflux rate constant in the severe preeclamptic women. There was no difference between the two hypertensive groups in intraerythrocyte sodium content during pregnancy. Ten of the women with chronic hypertension were followed sequentially at gestational week 24, 30, and 36; and 10 hypertensive women were also studied postpartum. There was a significant decrease in intraerythrocyte sodium and an increasing sodium efflux rate constant with increasing gestational age. When studied postpartum a restitution was attained in such a way that women with preeclampsia showed an increase in sodium efflux rate constant and a decrease in intraerythrocyte sodium whereas women with chronic hypertension increased in intraerythrocyte sodium content. Conclusion: An increase in sodium efflux rate constant and a decrease in cellular sodium content were seen in chronic hypertensive pregnancies with increasing gestational age. In severe preeclampsia sodium efflux rate constant was depressed and cellular potassium content diminished in the third trimester. Restitution of cellular sodium homeostasis was obtained postpartum.