Metabolism of Thiamine-S 35 in the Rabbit. ∗

Abstract

Summary

The fate of thiamine, labeled with sulfur-35 in the thiazole moiety, has been studied in rabbits after oral and parenteral administration of doses in the physiological range. Analyses of the urinary and fecal sulfur fractions for 4 to six 24-hour periods following administration of radiovitamin, gave average total recovery of radiosulfur of 77% after administration by stomach tube, 86% after intramuscular injection, and 54% after intravenous injection. When oral dose of radiovitamin was followed 6 hours later by intramuscular injection of a 20-fold larger dose of non-radioactive thiamine, an additional 17% of radiosulfur was recovered in urine. In all cases, the neutral sulfur fraction of urine contained more than 50% of the recovered radiosulfur, and the greater portion of this was excreted in the first 24-hour period following administration of radiovitamin. Isolation of main metabolites following oral administration indicates that unchanged thiamine-S³⁵ and thiazole S³⁵ moiety together account for approximately 95% of radiosulfur of the neutral sulfur fraction in the first 24-hour period, and are excreted in a ratio of 2 : 1, respectively.