Differentiation-Arrested Rat Fetal Lung in Primary Monolayer Cell Culture. III. Antioxidant Enzyme Activity

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Abstract
Differentiation-arrested monolayer lung cell cultures were developed from day 18, 20, and 22 rat fetuses and 3-day-old neonatal rats. These cultures were examined for antioxidant enzyme activity, and the values obtained were compared with previously reported in vivo activity. All cultures were catalase deficient, and activity could be restored by the addition of 0.25 μM Fe(NO3)3 · 9H20 to the culture medium. The other measured antioxidant enzymes–copper-zinc and manganese superoxide dismutase, glutathione peroxidase, and glucose 6-phosphate dehydrogenase–demonstrate gestation-dependent increases of activity in vivo that were not evident in vitro, supporting the concept of a circulating “maturation factor” during fetal life. When cultures from fetal days 20 and 22 and from neonatal day 3 lungs were challenged with 50% oxygen in the presence of serum, antioxidant enzyme activities were unchanged, and there was no evidence of cell damage as assessed by release of lactate dehydrogenase. In the absence of serum, however, fetal day 20 (but not fetal day 22 or neonatal day 3) lung cells showed evidence of cell damage and increased antioxidant enzyme activities. It is concluded that cultured immature fetal lung cells are more susceptible to oxygen toxicity than those derived from mature fetal or neonatal animals. This increased susceptibility cannot be explained on the basis of the reduced antioxidant enzyme activity observed in vivo.