1,25-Dihydroxyvitamin D3 metabolism in a human osteosarcoma cell line and human bone cells.
The metabolism of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] by a human osteoblastic sarcoma cell line, U-2 OS, and by primary cultures of human bone-derived cells was examined at physiologic (5 x 10(-11) M) and pharmacologic (3.5 x 10(-7) M) substrate concentrations. For metabolite identification purposes, cells nearing confluency were incubated for 18 h with 3.5 x 10(-7) M 1,25-(OH)2D3 in serum-free medium. The putative vitamin D metabolites produced during this incubation were isolated from a total lipid extract of cells and medium. Identification of the metabolites was achieved by comigration with authentic standards on three high-performance liquid chromatography systems, UV spectral analysis, mass spectrometry, and chemical modification by sodium borohydride and sodium metaperiodate. The identified metabolites produced from 1,25-(OH)2D3 by the human osteosarcoma cells include 1,24,25-trihydroxyvitamin D3; 24-oxo-1,25-dihydroxyvitamin D3; 24-oxo-1,23,25-trihydroxyvitamin D3; and 24,25,26,27-tetranor-1,23-dihydroxyvitamin D3. Evidence is presented that (1) 1,25-(OH)2D3 metabolism occurs constitutively in U-2 OS osteosarcoma cells at a physiologic substrate concentration (5 x 11(-11) M), (2) the pathway can be further induced by pharmacologic 1,25-(OH)2D3 concentrations (10(-7) M), and (3) this pathway is present in primary cultures of normal human bone-derived cells.
Miller
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BE
Norwich Eaton Pharmaceuticals, Inc., NY.
Chin
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DP
Jones
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D001842:Bone and Bones / Q000166:cytology / Q000378:metabolism*; D002117:Calcitriol / Q000378:metabolism*; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D008055:Lipids / Q000302:isolation & purification; D013058:Mass Spectrometry; D012516:Osteosarcoma / Q000378:metabolism*; D010504:Periodic Acid; D014297:Trimethylsilyl Compounds; D014407:Tumor Cells, Cultured
D008055:Lipids; D014297:Trimethylsilyl Compounds; D010504:Periodic Acid; C009288:metaperiodate; D002117:Calcitriol