Abstract
The effects of TSH and thyroxin on the metabolism of vitamin B_<12>-^<6〓>Co were studied on male Wistar strain rats. The absorption of orally administered B_<12>-^<6〓>Co was decreased following sither hypophysectomy or thyroidectomy, giving the rates of 47.7±2.8 and 38.4±5.0%, respectively, as compared to 66.4±4.6% in normals. These diminutions could be corrected with TSH or thyroxin, but not with intrinsic factor. In hyperthyroidal state, there was no remarkable difference in the absorption pattern. The fecal excretion of radioactivity following subcutaneous administration of B_<12>-^<6〓>Co increased to 19.3% after thyroidectomy, and decreased to 13.0% after thyroxin administration, when as it was 16.3% in controls. The urinary excretion of radioactivity was correlated with intestinal absorption at oral adminiatration test, and no remarkable hormonal effect could be found after subcutaneous administration test. The hepatic uptake of B_<12>-^<6〓>Co decreased in thyroidectomized state and increased in hyperthyroidal state, but after an excessive administration of thyroxin the hepatic uptake tended to decrease, though no effect was seen upon renal uptake. It could be concluded that the intestinal absorption of vitamin B_<12> was disturbed both in thyroidectomized and in hypophysectomized rats. And further it seems probable that the disturbance of vitamine B_<12> metabolism in hypophysectomized rats may be due to the loss of thyroidal function.
