POSSIBLE MECHANISM FOR LATE GESTATIONAL DEVELOPMENT OF THE ANTIOXIDANT ENZYMES IN THE FETAL-RAT LUNG

We hypothesized that a possible mechanism to explain the significant i ncreases that occur in the pulmonary antioxidant enzyme (AGE) system l ate in gestation might be an endogenous increase in the normal reactiv e O-2 substrates for these enzymes, We found that lung O-2 free radica l formation increased similar to 175% between fetal day 18 and birth ( p < 0.01), We also found that late fetal rat lung mitochondrial and mi crosomal rates of AOE substrate (H2O2) generation increased markedly, and there was also significantly increased lung lipid peroxidation pro ducts with increasing gestational age. These definite elevations in re active O-2 species production in parallel with the time course of matu rational elevations in the pulmonary AOE system, suggest that increasi ng enzyme substrate concentrations could be a primary controlling mech anism for increasing lung AOE gene expression in preparation for birth of the newborn.