Energy metabolism and function of thyroid gland in vitro.

Abstract

To obtain the information concerning the relation between the hormone synthetic function and metabolisms of thyroid gland, effects of some metabolic in hibitors upon oxidative, iodine and phosphorus metabolism of surviving beef and dog thyroid slices were studied with the uses of radioactive iodide (I131) and orthophosphate (P32). The main results obtained are as follows:1. Potassium cyanide (1×10-3M) shows remarkable inhibiting effect, in the same grade, upon oxygen consumption (“oxidation”), I131 uptake, iodine metabolism (“iodination”) and incorporation of radioactive phosphate into acid-soluble organic phosphate fraction (“phosphorylation”) of beef thyroid slice.2.2, 4-Dinitrophenol (DNP) in the concentrations of 1×10-5M, augments “oxidation”, while it inhibits “iodination” and “phosphorylation” of beef thyroid slice to a similar extent, showing an intimate relation between phosphorylation and iodination. In higher concentrations (5×10-5 to 1×10-4M) DNP decreases “oxidation” as well as “iodination” and “phosphorylation”.3. Methylthiouracil (MTU) in concentrations of 1×10-4 to 1×10-3M, has no effect on “oxidation” while it shows completely blocking effect on organic binding of iodine. However, “phosphorylation” is slightly inhibited by MTU (1×10-4M) and is inconsiderably increased in lower concentration (1×10-4M). In accordance with decrease of phosphorylation, iodination is also inhibited by MTU (1×10-3M).4. Glucose (100mg/dl), succinate (0.01M) and glutamate (0.01M) decrease “iodination” of dog thyroid slice despite increase of “oxidation” in the case of succinate. “Phosphorylation” of beef thyroid slice is not affected by the additions of glutamate and succinate. Glucose exerts an increasing effect of “phosphorylation”.5. The significance of the present results on the relation between energy metabolism and function of thyroid gland was discussed.