Abstract
In vivometabolism of intravenously injected monoiodotyrosine, diiodo-tyrosine and inorganic iodide was studied on thyroidectomized rats. Injected iodotyrosines disappear very rapidly from the circulation. The half-life for circulating monoiodotyrosine, diiodotyrosine and inorganic iodide was estimated as 30, 60 and 130 mins., respectively. These values reflect the rates of distribution, deiodination and excretion of the respective substances. Studies on the distribution and degradation of injected iodocompounds in several tissues clarified the metabolic fate of these substances In vivo. Iodotyrosines which enter tissues are rapidly deiodinated, and liberated iodide is returned into the circulation. The liver and kidney accumulate and deiodinate iodotyrosines rapidly. The kidney and stomach appear to concentrate and excrete iodide liberated from iodotyrosines. The small intestine is likely to absorb iodocompounds excreted in the gastric juice and bile. On the basis of the present study on the rat, it is not likely that a large amount of iodotyrosines is present in the normal human sera, though the presence of a minute amount is not excluded.
