Tissue Conversion of Thyroxine to Triiodothyronine.

Abstract

Summary (1) I¹³¹-labeled thyroxine was administered intravenously to normal and thyroidectomized rats and the animals sacrificed at varying time intervals thereafter. Specimens of liver, kidney and muscle were homogenized, extracted with butanol and the extracts were subjected to kieselguhr chromatographic analysis. Small amounts of triiodothyronine were recovered from all 3 tissues in about 20% of the analyses carried out. (2) When triiodothyronine was administered and the tissues subjected to the same conditions, no thyroxine was recovered. (3) When the tissues of rats given thyroxine were homogenized and subjected to fractionation into their subcellular components, triiodothyronine was more readily recovered than was the case where the whole homogenate was used. A possible explanation for this is discusses.