Pulmonary superoxide dismutase activity in the euthyroid and hypothyroid ovine fetus

Pulmonary superoxide dismutase (SOD) activity was measured in 11 euthyroid and 15 hypothyroid ovine fetuses at 130 days gestation. In the euthyroid fetus, the mean pulmonary SOD activity was similar in saline- and thyroxine-infused groups. Compared to the euthyroid fetus, the mean pulmonary SOD activity was significantly lower in the noninfused or saline-infused athyrotic fetus. Administration of thyroxine to the hypothyroid fetus results in a normalization of pulmonary SOD activity to control values. Thus, thyroxine appears to influence the maturation of pulmonary SOD activity in the ovine fetus during the third trimester.