Action of Cortison on the Utilization of Thyroid Hormones into the Organs

Cortisone may induce not only certain changes in the metabolism of various body substances, such as protein. carbohydrate, and electrolytes etc., but also the alteration of iodine metabolism in the thyroid gland and the extrathyroidal system. The present study. therefore. aimed to investigate the effect of cortisone administration on the distribution and the fate of triiodothyronine and thyroxine in the various organs. Following the injection of Jl31-labeled-I-triiodothyronine and Jl31-labeled-l-thyroxine into the cortisone treated mice and rabbits, the uptake of those subst· ances on the various organs and the disappearance of blood radioactivity were observed. And the effect of cortisone was studies by the uptake of 113l.)-triiodothyronine into erythrocytes and the uptake of Jl31·I·thyroxine on the survival slices of liver and kidney cortex in vitro. From these experiments, it was found that the uptake of 1131·I·triiodothyronine and 1131·I-thyroxine on the liver. heart and kidney cortex was decreased significantly by the administration of cortisone in the mice while the disappearance of blood radioactivity was not altered significantly after the injection of 1131·I·thyroxine into the rabbits. There was not any significant differences in the inhibition of uptake between Jl3l.)-triiodothyronine and 1131·I-thyroxine. The uptake of Jl31·I·triiodothyronine into the erythrocytes was not altered significantly by the massive adminstration of cortisone in the rats, but the uptake of red cells from the cortisone treated animals was decreased by the exchange of media with normal plasma. The uptake of 1131·I-thyroxine on the liver and the kidney cortex of rat depended on the characteristics of incubation media. The survival slices of liver and kidney cortex showed high uptake of thyroxine in the normal saline while the uptake was decreased significantly in the rabbit plasma. Following the massive injection of cortisone. the uptake of I·thyroxine in the survival slices was increased in the normal saline but it was decreased in the rabbit plasma. And the possible mechanism of cortisone effects on the distribution and uptake of thyroid hormone was also discussed