INCREASED ASCORBATE RADICAL FORMATION AND ASCORBATE DEPLETION IN PLASMA FROM WOMEN WITH PREECLAMPSIA - IMPLICATIONS FOR OXIDATIVE STRESS

There is evidence that oxidative stress accompanies preeclampsia and p lasma ascorbate concentrations are reported to be decreased in the dis order. We tested the hypothesis that an ascorbate-oxidizing activity i s increased in plasma from women with preeclampsia relative to normal pregnancy. Electron paramagnetic resonance (EPR) spectroscopy was used to determine (1) plasma functional reserves of ascorbate and total th iols, (2) temporal changes in ascorbate and thiol concentrations durin g incubation of whole blood in vitro, and (3) ascorbate radical signal kinetics in plasma after equalization of ascorbate concentrations. Hi gh-pressure liquid chromatography (HPLC) was used to measure plasma al pha-tocopherol. Ascorbate concentrations were 50 % lower in preeclamps ia relative to normal pregnancy plasma but thiols and alpha-tocopherol did not differ, The elapsed time prior to half-consumption of plasma ascorbate was decreased approximately three-fold during incubation of whole blood from preeclamptics. No concomitant decrease in thiols was evident. The initial ascorbate radical signal amplitude was greater in preeclampsia plasma and then, in contrast to normal pregnancy plasma, decreased progressively. The iron chelator, deferoxamine had no effec t on plasma ascorbate radical formation. We conclude that an ascorbate -oxidizing activity is increased in preeclampsia plasma which might co ntribute to vascular dysfunction in the disorder. (C) 1997 Elsevier Sc ience Inc.