The turnover of thiamine and its phosphate esters in rat organs.

Thiamine-deficient rats were injected with [(35)S]thiamine and the turnover of the injected radioactive thiamine and its phosphate esters was measured in brain, heart, and liver after returning the rats to a normal diet. The radioactivity per gram wet tissue, as well as the specific activity, fell to half its initial value in less than 40 hr, showing that thiamine compounds were turning over rapidly in the body under normal conditions. Furthermore, there was no difference in the rate of turnover of the individual phosphate esters of thiamine. The amount of the various phosphate esters as a percentage of the total thiamine remained the same throughout the experiment.