title: The isolation and identification of two new metabolites of 25-hydroxyvitamin D3 produced in the kidney.
abstract: We have demonstrated in this paper the isolation and identification of two new metabolites of 25-hydroxy-vitamin D3 (25(OH)D3) from the kidney of the vitamin D-replete rat. These are 24-oxo-23(25-(OH)2D3 and 24,25,26,27-tetranor-23(OH)D3. Both compounds logically fit on the same metabolic pathway. 25(OH)D3 leads to 24(R),25-(OH)2D3 leads to 24-oxo-25(OH)D3 leads to 24-oxo-23,25-(OH)2D3 leads to leads to 24,25,26,27-tetranor-23(OH)D3 Each metabolite on this pathway was isolated and identified from kidneys perfused with pharmacological concentrations of 25(OH)D3. All metabolites were identified by techniques involving high performance liquid chromatography, UV spectrophotometry, and mass spectrometry. Use of 24(R),25-(OH)2D3 as the substrate gave rise to increased amounts of 24-oxo-25(OH)D3, 24-oxo-23,25-(OH)2D3, and 24,25,26,27-tetranor-23(OH)D3. In vitro studies involving perfusion of a vitamin D-replete kidney with 25(OH)D3 at a concentration of 25 nM suggest that 24-oxo-23,25-(OH)2D3 is also formed under physiological conditions. At this substrate concentration, 24(R),25-(OH)2D3 represented the major metabolite accumulating in the perfusate over the initial 2-h period but at subsequent times the concentration of 24-oxo-23,25-(OH)2D3 increased so that by the end of 6 h it was the major product remaining in the perfusate. Our work also suggests that the rate of synthesis of 25(OH)D3-26,23-lactone is measurable in the intact mammalian kidney but that it is slower than the synthesis of 24(R),25-(OH)2D3 and its metabolites.
mesh_terms: D000818:Animals; D001711:Biotransformation; D002112:Calcifediol / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D013056:Spectrophotometry, Ultraviolet; D014808:Vitamin D Deficiency / Q000378:metabolism
chemical_list: D002112:Calcifediol