STUDIES ON THE EFFECT OF THYROXINE ADMINISSTRATION ON CATALASE ACTIVITY

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Abstract
Liver, kidney and blood catalase activity was determined on normal rats and rats receiving injections of thyroxine. Thyroxine administration produced a decrease in liver and kidney catalase activity, but no change was detected in blood catalasc activity. Addition of thyroxine or 3,5,3′-triiodo-L-thyronine to liver homogenates did not alter the enzyme activity. When liver homogenates from normal and thyroxine-treated rats were mixed, the catalase activity of the mixed homogenate was equal to the activities of the separate fractions. Measurement of the incorporation of Fc59 into liver catalase revealed a marked inhibition of radioiron utilization in thyroxine-treated animals. From these data it was concluded that the decreased catalase activity in the livers of thyroxine-treated rats was the result of an inhibition of enzyme formation.
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