Effect of Thyroid Hormone on Peroxisomal Flavin Enzymes in Rat Liver and Kidney

Abstract

The Effect of thyroid hormone on peroxisomal enzyme activity was studied in thyroidectomized-and T₄-administered-thyroidectomized rats. In liver, the activities of isozyme A of L-a-hydroxyacid oxidase, D-amino acid oxidase, urate oxidase and catalase were decreased by thyroidectomy, and the diminished enzyme activities were restored by T₄ administration to rats. These modifications induced by thyroidectomy or by T₄ administration, however, were prominent only in immature animals (20-day-old rats). Although the changes in-a-hydroxyacid oxidase and D-amino acid oxidase activities, induced by thyroidectomy or by T₄ administratration, were also observed in 40-day-old rats, those in urate oxidase and catalase activities were not significant in 40-dayold rats. Acyl CoA oxidase activity was not affected by thyroidectomy or by T₄ administration in either 20-or40-day-old rats. In the kidney, isozyme B of L-α-hydroxiacid oxydase activity was reduced by thyroidectomy and thediminished enzyme activity was restored by T₄ administration in both20-and 40-day-old rats. D-Amino acid oxidase and catalase activities in kidney, however, were not significantly modified by throidectomy or by T₄ administration in either20-or40-day-old rats. The results suggest that thyroid hormone can modify the peroxisomal enzyme activity, which is prominent in immature animals.