Radioactive thiamin, C-2 of thiazole labeled with
14C, was parenterally administered to carp. After 24h, thiamin, its phosphate esters and thiazole in the eleven kinds of tissues and in the water of the aquarium, were fractionated by SP-Sephadex C25, and their radioactivities were measured. The radioactive thiamin was used to synthesize thiamin phosphate esters, mostly thiamin diphosphate (TDP), retained as a free form of thiamin, or decomposed to thiazole. The ratios of
14C-TDP to the total incorporated radioactivity in the ordinary muscle, kidney, and red muscle were 47, 42, and 34%, respectively. The eye tissue contained
14C-thiamin corresponding to over 50% of total incorporated radioactivity, which was very different from the other tissues. The ratios of
14C-thiazole, a decomposed product of
14C-thiamin, was highest in the kidney, followed by the gill and the heart. Furthermore, the amount of
14C-thiazole excreted into the water of the aquarium was ten times more than that in these tissues. To ascertain whether thiazole was truly produced by tissue such as liver,
14C-thiamin was added to cultured carp hepatocytes, and the radioactivities were analyzed both in the cell and in the medium by the same method. After 24h incubation,
14C-thiazole was mainly found in the medium, while no production of
14C-thiazole was observed in control experiments, in which
14C-thiamin was added to the cells treated with trichloroacetic acid or to the medium without hepatocytes. Furthermore, cultured hepatocytes produced
14C-TDP corresponding to 71% of total radioactivity incorporated in the cells. These results indicate that thiazole is produced by carp liver
in vivo, and thiamin phosphate esters, especially TDP, are also synthesized from thiamin.
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