Impact of diabetes on sodium-lithium countertransport in pregnancy-induced hypertension.

The purpose of this study was to assess the impact of type I diabetes on sodium-lithium countertransport (CTT) in normotensive third trimester women and those with pregnancy-induced hypertension (PIH). CTT was measured in the following groups: nonpregnant diabetic and nondiabetic women, pregnant nondiabetics with and without PIH, and pregnant diabetics with and without PIH. CTT was determined as external sodium-stimulated lithium efflux from lithium loaded red cells [mmoles/liter of cells x hours = units (U)]. In the nonpregnant state, nondiabetics and diabetics demonstrated similar CTT activity (0.20 +/- 0.02 U, n = 22, v 0.26 +/- 0.03 U, n = 18). In pregnancy, normotensive nondiabetics and diabetics had CTT activity similar to each other, the values of both being significantly higher than those in nonpregnant women (0.39 +/- 0.03 U, n = 26, v 0.46 +/- 0.05 U, n = 17). Nondiabetics with PIH demonstrated higher CTT (0.53 +/- 0.03 U, n = 30) than normotensive pregnant nondiabetics (P = .002). However, diabetics with PIH and CTT activity (0.48 +/- 0.04 U) indistinguishable from normotensive pregnant diabetics (0.46 +/- 0.05 U). There were no differences in gestational age, renal function, or glycohemoglobin that could explain these observations. Therefore, we conclude that PIH in type I diabetic women, in contrast to PIH in nondiabetic pregnant women, is not associated with a further elevation in CTT.