Studies on Absorption, Distribution, Excretion and Metabolism of ^3H-1α-Hydroxycholecalciferol in Rat

Abstract

The absorption, distribution, excretion and metabolism of 2-^3H-1α-OH-D_3 (4.2 Ci/mmol) were studied in rat after oral or intravenous dosing. (1) Peak blood level of administered radioactivity was observed at 10 hours after oral administration with apparent half life of 2.4 days whereas that was 2.3 days after intravenous administration. (2) Administered radioactivity was distributed relatively high in the liver, while any other specific distribution or accumulation was not observed in the another tissues. (3) Together with the results of excretion studies, it revealed that major part (91%) of radioactivity administered via intravenous route recycled enterohepatically finally excreted to feces. (4) Appleciable amount of ^3H-1α, 25-(OH)_2-D_3 could be detected in all tissues and body fluids examined after both oral and intravenous dosing using Sephadex LH-20 column chromatography, suggesting that this compound was the main metabolite in rat.