PMID: 6973569Aug 10, 1981Paper

Human bone cells in culture metabolize 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3 and 24,25-dihydroxyvitamin D3.

The Journal of Biological Chemistry
G A HowardD J Baylink

Abstract

Bone cells respond to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) for mineral mobilization and contain receptors for 1,25(OH)2D3. We report here the expression of 25-hydroxyvitamin D3 (25 (OH)D3) metabolizing enzymes in primary cultures of human bone cells, as well as n a human osteosarcoma cell line. Human bone cells were obtained by enzyme digestion of the extracellular matrix of bone from iliac crest biopsies from 3 male patients without primary bone disease. These cells were plated (5 X 10(4)/min) in medium with 10% fetal calf serum and proliferated to confluence in 10-14 days. At confluence, the medium was replaced with serum-free medium. The cells were preincubated in this serum-free medium for 24 h prior to incubating them 2-4 h with [3H]25(OH)D3 (10-20 nM). The vitamin D metabolites synthesized during this incubation were extracted from the medium and cells with dichloromethane, then separated by chromatography on Sephadex LH-20, followed by high performance liquid chromatography. The cells synthesized 1,25(OH)2D3 and 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) with the specific activities of the 1- and 24-hydroxylases similar in magnitude to those in kidney cells in vitro. The enzymes could be regulated by external perturbatio...Continue Reading

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