title: Metabolism and pharmacokinetics of 24,25-dihydroxyvitamin D3 in the vitamin D3-replete rat.
abstract: The time course of in vivo metabolism of 24,25-dihydroxyvitamin D3 in rats has been examined. Several tissues were surveyed in an effort to discover new metabolites of 24,25-dihydroxyvitamin D3 and to estimate the concentrations of previously identified metabolites. Rapidly growing male rats were dosed with 24,25-dihydroxyvitamin D3 orally until plasma concentrations of 24,25-dihydroxyvitamin D3 were at steady state. 24,25-Dihydroxyvitamin [3-3H]D3 was then administered. At 10 min and 1, 6, 15, 24, 96, and 192 h after dosing, the animals were killed, and plasma, liver, intestine, and bones were analyzed with a newly developed gradient straight-phase high performance liquid chromatography system. The high performance liquid chromatography system is capable of base-line resolution of most of the major vitamin D metabolites. 24,25-Dihydroxyvitamin D3 clearance from plasma, liver, and kidney but not intestine followed a two-compartment model. 24,25-Dihydroxyvitamin D3 disappeared from plasma with a half-life of 0.55 h (fast phase) and 73.8 h (slow phase). Only two lipid-soluble metabolites of 24,25-dihydroxyvitamin D3 were detected: 24-oxo-25-hydroxyvitamin D3 and 1,24,25-trihydroxyvitamin D3. These compounds circulate at very low concentrations in the plasma (50 pg/ml of plasma).
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3; D000818:Animals; D001842:Bone and Bones / Q000378:metabolism; D002762:Cholecalciferol / Q000378:metabolism*; D004100:Dihydroxycholecalciferols / Q000378:metabolism*; D006207:Half-Life; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008297:Male; D051381:Rats; D014316:Tritium
chemical_list: D004100:Dihydroxycholecalciferols; D014316:Tritium; D002762:Cholecalciferol; D015650:24,25-Dihydroxyvitamin D 3