Effects of thyroid hormones, antithyroid drugs and iodide on in vitro conversion of thyroxine to triiodothyronine.
In an attempt to study the effects of thyroid hormones, antithyroid drugs and iodide on the conversion of thyroxine (T4) to triiodothyronine (T3), the liver was obtained from normal, hypothyroid and hyperthyroid rats treated with T4 or T3 . T4 was incubated with liver homogenates and generated T3 was measured. 1. The conversion of T4 to T3 was less in the liver homogenates from thyroidectomized, methylmercaptoimidazole (MMI)-treated and propylthiouracil (PTU)-treated rats. The magnitude of decrease was the same in thyroidectomized and MMI-treated rats, but was greater in PTU-treated rats. 2. Administration of T4 and T3 to thyroidectomized and MMI-treated rats restored the converting activity. When excess T4 was administered, the converting activity was above normal. In contrast, administration of graded doses of T4 failed to restore the converting activity of the liver from PTU-treated rats. 3. In vitro addition of MMI failed to affect converting activity of the liver, but addition of excess iodide and PTU significantly depressed it.
D000818:Animals; D013956:Antithyroid Agents / Q000494:pharmacology*; D007037:Hypothyroidism / Q000378:metabolism; D066298:In Vitro Techniques; D007455:Iodine / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism; D008297:Male; D051381:Rats; D013963:Thyroid Hormones / Q000494:pharmacology*; D013965:Thyroidectomy; D013974:Thyroxine / Q000378:metabolism*; D014284:Triiodothyronine / Q000096:biosynthesis*
D013956:Antithyroid Agents; D013963:Thyroid Hormones; D014284:Triiodothyronine; D007455:Iodine; D013974:Thyroxine