Regulation of the sodium pump in pregnancy-related tissues in preeclampsia

OBJECTIVE: This study examined the expression of the three α-isoforms of the sodium pump in preeclampsia. Reductions in sodium pump number and activity in smooth muscle may underlie hypertension in preeclampsia. STUDY DESIGN: Northern and Western analyses were used to determine whether sodium pump α-isoform regulation in myometrium, placenta, and umbilical artery of women with preeclampsia differed from those with normotensive pregnancies. RESULTS: Levels of α1 and α3 messenger ribonucleic acid were reduced in myometrium of women with preeclampsia compared with normotensive pregnancies, as was α2 messenger ribonucleic acid in preeclamptic placenta. Protein expression of the α-isoforms was unaltered in placenta and umbilical artery from women with preeclampsia versus those with normotensive pregnancies, but myometrial α2 protein levels were reduced significantly in women with preeclampsia. Moreover, myometrial α1 protein expression was undetectable. CONCLUSIONS: Reduced smooth muscle sodium pump expression in preeclampsia may raise cell sodium, increase pressor sensitivity, or increase tone directly, which may contribute to hypertension in preeclampsia.