甲状腺のTSH receptorに関する研究 : TSH刺激に対するconcanavalin Aの2相性効果とそのpositive cooperativity

概要

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Concanavalin A (Con A) was tested for its ability to affect thyroid activation induced by the thyroid stimulators in mouse thyroid tissues. Con A was found to have the biphasic stimulatory and inhibitory effects on thyrotropin (TSH) -induced cyclic AMP formation and endocytosis, a step in thyroid hormone secretion, in mouse thyroid tissues. Low concentrations of Con A potentiated TSH-stimulated cyclic AMP formation and endocytosis. In contrast, high concentrations of Con A markedly inhibited TSH stimulations. These effects were reversed by the addition of methyl-alpha-D-glucoside to the second preincubation medium (without Con A) prior to TSH. A high concentration of Con A alone did not depress the basal levels of cyclic AMP or basal glucose oxidation in thyroid tissues. A high concentration of Con A also inhibited cyclic AMP formation induced by prostaglandin E2 and the long-acting thyroid stimulator (LATS). Binding of 125I-labeled Con A to thyroid tissues increased with time up to 7 5 min and was very slowly reversible after attainment of equilibrium. Binding was directly proportional to tissue weight. Scatchard plot analysis on the binding of 125I-labeled Con A to thyroid tissues indicated a positive cooperativity which seemed to be well correlated to the biphasic effects.
日本内分泌学会の論文