NEUROPROTECTIVE EFFECT OF PHENYTOIN AGAINST IN-UTERO HYPOXIC BRAIN INJURY IN FETAL GUINEA-PIGS

The present study tests the hypothesis that phenytoin, an antiepilepti c agent known to block Na+ and Ca2+ channels, will prevent hypoxic bra in injury in the fetus by preventing lipid peroxidation and preserving Na+,K+-ATPase activity. Studies were performed in 37 fetuses obtained from pregnant guinea pigs at 58-60 days,gestation (term). The pregnan t guinea pigs were divided into four groups: a normoxic group, a hypox ic group, a normoxic group treated with phenytoin, and a phenytoin tre ated hypoxic group. There were eight to ten fetal guinea pigs in each group. The treatment groups were given phenytoin 30 mg/kg (50 mg pheny toin/ml solvent) intraperitoneally. Hypoxia was induced by exposing th e guinea pigs to 7% oxygen for 60 min. This level of hypoxia has been shown to decrease ATP and phosphocreatine levels by 90%. The fetal bra ins were harvested and the brain cell membranes were prepared from eac h group of fetuses. Na+,K+-ATPase activity and lipid peroxidation prod ucts, measured as relative fluorescent intensity, were determined. The mean Na+,K+-ATPase activity in the control, hypoxic, phenytoin-normox ic and phenytoin-hypoxic groups was 56.4+/-9.7, 37.9+/-10.6, 47.0+/-8. 4 and 52.0+/-9.7 mu mol inorganic phosphate/mg protein per h, respecti vely. The hypoxic group had significantly less Na+,K+-ATPase activity than both the normoxic group (P < 0.01), and the phenytoin treated hyp oxic group (P < 0.05). There was no significant difference between the normoxic group and either of the phenytoin-treated groups (P = ns). T he mean relative fluorescent intensity, measured in mu g quinine sulfa te/g brain, was higher in the hypoxic, 1.85+/-0.36, than in the normox ic group, 1.25+/-0.10 (P < 0.05). There was no significant difference between the phenytoin-hypoxic group (1.53+/-0.35) and the phenytoin-no rmoxic group (1.50+/-0.45; P = ns). Exposure to hypoxia caused a decre ase in Na+,K+-ATPase activity and an increase in lipid peroxidation of fetal brain cell membranes. Treatment with phenytoin before exposure to hypoxia prevented these changes, preserving brain cell membrane str ucture and function. These data suggest that administration of phenyto in prior to in utero hypoxia may be neuroprotective.