title: The biphasic stimulatory and inhibitory effects of concanavalin A on thyroid activation induced by thyrotropin.
abstract: Concanavalin A (Con A) was tested for its ability to affect thyroid activation induced by TSH in mouse thyroid lobes. Pretreatment of thyroid lobes with Con A at concentrations from 1.55--400 microgram/ml was found to have biphasic stimulatory and inhibitory effects of the TSH-induced accumulation of cAMP and formation of colloid droplets. Low concentrations of Con A potentiated TSH activation of thyroidal formation of cAMP and endocytosis. In contrast, higher concentrations of Con A markedly inhibited these TSH effects. The inhibitory effects observed after preincubation with Con A were abolished by the addition of alpha-methyl-D-glucoside to the incubation medium. A high concentration of Con A also inhibited cAMP formation induced either by prostaglandin E2 or the long-acting thyroid stimulator. However, the basal and TSH-stimulated glucose oxidation in mouse thyroid lobes was not depressed by a high concentration of Con A. Uptake of 125 I-labeled Con A by thyroid tissues increased with time up to 1 h and was directly proportional to tissue weight. These findings suggest that the specific interaction between Con A and its receptors may lead to conformational changes in the structure of the membranes of the thyroid follicular cells which facilitate TSH-induced thyroid hormone secretion via the adenylate cyclase-cAMP system.
mesh_terms: D000818:Animals; D003208:Concanavalin A / Q000378:metabolism / Q000494:pharmacology*; D000242:Cyclic AMP / Q000096:biosynthesis; D005947:Glucose / Q000378:metabolism; D008135:Long-Acting Thyroid Stimulator / Q000494:pharmacology; D008297:Male; D008757:Methylglucosides / Q000494:pharmacology; D051379:Mice; D011458:Prostaglandins E / Q000494:pharmacology; D011952:Receptors, Concanavalin A / Q000378:metabolism; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism; D013963:Thyroid Hormones / Q000378:metabolism; D013972:Thyrotropin / Q000494:pharmacology*
chemical_list: D008757:Methylglucosides; D011458:Prostaglandins E; D011952:Receptors, Concanavalin A; D013963:Thyroid Hormones; D003208:Concanavalin A; D013972:Thyrotropin; D008135:Long-Acting Thyroid Stimulator; D000242:Cyclic AMP; D005947:Glucose