CONJUGATES OF TRIIODOTHYRONINE AND ITS METABOLITES1

Compounds a and b, previously described as major metabolites formed in the dog from 3,5,3′-I131 triiodothyronine (T3), have been identified by enzymatic and chromatographic technics as T3 sulfate and 3,3′ T2 sulfate. These sulfoconjugates occur together in the bile in amounts equal to or greater than that of T3 glucuronide; and with a third, but unidentified, sulfate they account for 90% of the I131 excreted in the urine by the dehepatized dog after the injection of radioactive T3. The major metabolite of T3 in blood and urine of the dehepatized dog is 3,3% T2 sulfate. Deiodination of T3 by extrahepatic tissues is extensive, but it involves chiefly the removal of iodine (nonradioactive in the compound given) from the benzene ring with the alanine side chain, and to a very limited extent, the I131 from the phenolic ring.