Binding of thyroxine with subcellular components of brain, liver and tail tissues of Rana pipiens tadpoles

Abstract

Binding of radioiodinated thyroxine given in vivo was measured in subcellular fractions of liver, tail and brain tissues of premetamorphic tadpoles of Rana pipiens. Binding at 6 hr after hormone injection was measured in otherwise untreated tadpoles, or in animals given various additional quantities of unlabeled hormone up to 1000 times the dose of labeled hormone. In all tissues increasing doses of cold hormone depressed binding or accumulation of labeled hormone in cytosol or nuclear fractions, but some of the binding was not saturable. Thyroid hormone binding in brain cell nuclei was almost completely of the saturable type, and in this sense, it differed from liver and tail tissues.