Influence of Superoxide Dismutase and Catalase on the Stimulation by Phagocytosis of L-Thyroxine and L-Triiodothyronine Deiodination in the Human Leukocyte

Neither superoxide dismutase, which destroys the superoxide radical by catalyzing its conversion to hydrogen peroxide, nor catalase prevented the stimulation by phagocytosis of the deiodination ofL-thyroxine orL-triiodothyronine in human leukocytes. On the other hand, superoxide dismutase led to an increase in the proportion of iodinated material, which remained at the 6rigin during chromatography in a butanol-acetic acid-water solvent system, whereas catalase had the opposite effect. The data suggest that neither the superoxide radical nor hydrogen peroxide plays a major role in the stimulation of deiodination of hormone, but that once deiodination has occurred, hydrogen peroxide is more important than the superoxide radical in subsequent iodination reactions within the leukocyte.