title: Regulation of calcium fluxes in the thyroid.
abstract: Calcium (Ca2+) exchanges were studied in dog thyroid slices incubated in vitro. With 45Ca2+-prelabeled slices, carbamylcholine 10(-7)-10(-5) M (Cchol) induced an important transitory spike efflux, inhibited by procaine and atropine while the stimulated efflux obtained with high concentrations of TSH (10 mU/ml) was progressive and sustained over time. The effects observed with both agents did not require extracellular Ca2+ and were insensitive to verapamil 10(-6)-10(-4) M. Neither dibutyryl (Bu2)-cAMP, nor any agent raising intracellular cAMP (prostaglandin E2, choleratoxin, inhibitors of phosphodiesterases with low concentrations of TSH) were able to reproduce the action of TSH 10 mU/ml, forskolin 10(-5) M being the only exception. Replacement of sodium by choline (+ atropine) in the incubation medium decreased the basal efflux and inhibited the TSH effect. Ouabain 10(-3) M also abolished the TSH-induced Ca2+ efflux, while having no influence on carbamylcholine action. TSH 10 mU/ml and 1 mU/ml, Bu2-cAMP 10(-3) M, choleratoxin and prostaglandin E2 with inhibitors of phosphodiesterase decreased the total 45Ca2+ uptake of the slices, while no effect of Cchol could be detected on this parameter. The results obtained suggest that (1) Cchol and TSH stimulate 45Ca2+ efflux from dog thyroid slices with different kinetics, by mobilization of intracellular Ca2+ stores; (2) this effect of TSH is not mediated by cAMP; (3) independently TSH at low concentrations (1 mU/ml), through cAMP, decreased 45Ca2+ uptake; this suggests that increased 45Ca2+ efflux and decreased uptake result from different mechanisms, as has been described for iodide exchange in FRTL-5 cells.
mesh_terms: D000262:Adenylyl Cyclases / Q000502:physiology*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D002772:Cholera Toxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D004285:Dogs; D066298:In Vitro Techniques; D010042:Ouabain / Q000494:pharmacology; D011343:Procaine / Q000494:pharmacology; D011458:Prostaglandins E / Q000494:pharmacology; D013961:Thyroid Gland / Q000502:physiology*; D013972:Thyrotropin / Q000494:pharmacology
chemical_list: D011458:Prostaglandins E; D011343:Procaine; D010042:Ouabain; D002217:Carbachol; D013972:Thyrotropin; D002772:Cholera Toxin; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D002118:Calcium