Thyroid hormone uptake by rat hepatocytes in primary culture

摘要: textabstractIodide is taken up by the thyroid follicular cell, oxydized and bound to thyroglobulin at apical membrane facing colloid in lumen. Iodinated subsequently engulfed the follicular cell hydrolysed, liberating thyroxine and triiodothyronine from their peptide linkage to thyroglobulin. Iodothyronines are then secreted into the blood stream. These other steps synthesis and secretion of hormones conditioned by extent stimulation pituitary thyrotropin. The synthesis release thyrotropin is stimulated hypothalamic thyrotropinreleasing hormone, while hormone inhibits these processes (Larsen, 1982). In this way, a negative feedback mechanism formed between thyroid and pituitary. The main product human is thyroxine (mean 115 nmol/day per 70 kg body weight). Other products 9 nrnol/day, which accounts for 20% total daily production) and reverse 2 nmol/day; 6%) (Chopra, 1976; Chopra et al., 1978a; Visser, 1980). From these figures it will be clear that of the latter iodothyronines occurs mainly outside the thyroid gland monodeiodination thyroxine, the so-called peripheral production. pathophysiological conditions, like iodine deficiency Graves' disease, thyroidal is increased relative thyroxine (Izumi and Larsen, 1977). contribution different tissues production triiodothyronine and present unknown. However, deiodination has been observed in vitro almost all tissues studied (see review by Visser, 1980). Based on circumstantial evidence, it is generally believed liver site of synthesise For instance, in liver cirrhosis decreased, while apparent synthesis is unaltered (Chopra, 1976). finding is favour extra-hepatic thyroxine_.reverse triiodothyronine conversion. low serum reverse triiodothyronine levels patients with severe, chronic renal failure may suggest substantial amounts produced in the kidneys (Chopra 1975; Weissel al., 1977; Stummvoll, 1981).