Metabolism of 3H-1 alpha,25-dihydroxyvitamin D3 in cultured human keratinocytes.
In the present investigation we studied the metabolism of 1 alpha,25-dihydroxy-[1 beta-3H]vitamin D3 (3H-1,25(OH)2D3) in culture-grown human keratinocytes (CHK). Our results showed that the cellular uptake of 3H-1,25(OH)2D3, upon incubation with CHK, occurred very rapidly; and it paralleled a decrease in the concentration of 3H-1,25(OH)2D3 in the medium. The amount of 3H-calcitroic acid, on the other hand, increased slowly in the medium, while the concentration of 3H-calcitroic acid in the cell remained undetectable during the whole period of incubation. When the cells were preincubated with 1,25(OH)2D3 (10(-8)M), conversion of 3H-1,25(OH)2D3 to 3H-calcitroic acid increased almost twofold, indicating that 1,25(OH)2D3 catalyzed its own catabolism.
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Vitamin D Skin and Bone Research Laboratory, Boston University School of Medicine, Massachusetts 02118, USA.
Ray
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Holick
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D002117:Calcitriol / Q000378:metabolism*; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism*; D012867:Skin / Q000166:cytology / Q000378:metabolism*; D014316:Tritium
D014316:Tritium; D002117:Calcitriol