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 trimest er 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 diabe tics with and without PIH. CTT was determined as external sodium-stimu lated lithium efflux from lithium loaded red cells [mmoles/liter of ce lls X hours = units (U)]. In the nonpregnant state, nondiabetics and d iabetics 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 demon strated higher CTT (0.53 +/- 0.03 U, n = 30) than normotensive pregnan t nondiabetics (P =.002). However, diabetics with PIH had CTT activity (0.48 +/- 0.04 U) indistinguishable from normotensive pregnant diabet ics (0.46 +/- 0.05 U). There were no differences in gestational age, r enal function, or glycohemoglobin that could explain these observation s. Therefore, we conclude that PIH in type I diabetic women, in contra st to PIH in nondiabetic pregnant women, is not associated with a furt her elevation in CTT.