Studies of metabolic turnover with tritium as a tracer. II. Gross studies on the rat.

Previous papers in this series have dealt with the gross metabolic turnover of tritium-labeled compounds in whole mice (1) and in various organs and tissues of rats (2). The present study extends these findings to specific compound fractions isolated from rat tissues. Attention is directed toward the compounds of very slow turnover rate which retain appreciable tritium label from 4 to 8 months after tritium oxide administration. The results reported are of a screening nature and do not represent a thorough study of any particular one. They do indicate, however, an apparent wide-spread distribution of relatively inert compounds among a variety of different types. They also indicate that the same type of compound may exhibit widely different turnover rates in different tissues.