Maternal infusion of antioxidants (Trolox and ascorbic acid) protects the fetal heart in rabbit fetal hypoxia

The antioxidants, Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2 carboxylic acid, a water soluble analog of vitamin E) and ascorbic acid (AA), protect the heart from ischemia-reperfusion injury. We hypothesized that maternal infusion of Trolox and AA, would reduce the fetal bradycardia and myocardial damage observed in fetal hypoxia and increase the total antioxidant activity in fetal plasma. Either i.v. saline (control group) or Trolox + AA (drug group) was randomly administered to 29 d-old pregnant rabbits. Fetal hypoxia was induced by uterine ischemia. Fetal heart rate, plasma CK-MB activity, and plasma total radical antioxidant potential (TRAP) were measured in different sets of animals. Fetal heart rate in the drug group was higher than in the control group for the first 35 min (p < 0.05 at every 5-min interval). Fetal bradycardia (<60 beats/min) occurred after 39 min (median) in the drug group, and 29 min in the control group (p < 0.05). After 50 min of hypoxia, plasma CK-MB was lower in the drug group, 1204 ± 132 U/L (mean ± SEM), than in the control group, 2633 ± 233 U/L (p < 0.05), TRAP was higher in the drug group, 3.01 ± 0.15 mM (Trolox equivalent concentration), than in the control group, 1.48 ± 0.27 mM (p < 0.05). Higher TRAP levels (≥2.0 mM) were associated with lower CK-MB levels (<2500 U/L) (p < 0.05). Administration of Trolox and AA to the mother has a beneficial effect on fetal myocardial damage after fetal hypoxia, and a small beneficial effect on fetal bradycardia during hypoxia. The beneficial effect may be due to the augmentation of fetal plasma antioxidants from maternal antioxidant pretreatment.