THE DEIODINATIQN OF THYROXINE TO TRIIODOTHYRONINE BY KIDNEY SLICES OF RATS WITH VARYING THYROID FUNCTION1

Abstract
Previously reported deiodination of thyroxin to triiodothyronine in vitro by rat kidney slices is confirmed. The deiodinating system is heat labile, and is inhibited by thiouracil and triiodothyronine. The deiodination of thyroxin by kidney slices of rats with varying thyroid function was studied. Kidney slices of hyperthyroid rats showed greater deiodinating activity and hypothyroid rats less than normal. The presence of an adaptive thyroxin deiodinating enzyme system conditioned by the level of thyroxin in the tissue is postulated.