Protein Metabolism in Thyroid Glands of Euthyroid,Thiouracil-fed and Hypophysectomized Rats after Cortisone Treatment 1

Abstract

Summary

Chronic administration of cortisone (5 mg/day) to hypophysectomized pituitary replaced rats resulted in decreased: (a) body weight; (b) thyroid weight; (c) incorporation of ³H-leucine into thyroid protein; and (d) an increase in liver weight similar to that seen in unoperated rats injected with adrenocorticoids. These data indicate that cortisone is equally effective in intact and hypophysectomized rats receiving pituitary replacement therapy but argue against a major pituitary involvement. Incubation of thyroid gland lobes in vitro with ³H-inulin indicated that the extracellular gland space of thiouracil-fed rats was markedly reduced below that of either euthyroid or euthyroid plus cortisone animals (p>0.01). When thiouracil-fed rats were given cortisone their gland inulin space was not reduced as much, although it was still significantly smaller (p>0.05) than that of glands from rats of either euthyroid group. Cortisone treatment, however, had no effect on the inulin space in glands of euthyroid animals. The ability of ³H-cycloleucine to enter the thyroid gland intracellular pool under in vitro incubation condition was unaffected by any of the prior in vivo treatments. It is suggested that chronic cortisone treatment may affect thyroid gland protein biosynthesis indirectly by altering its available supply and pattern of amino acids.