Calvarial cells synthesize 1 alpha,25-dihydroxyvitamin D3 from 25-hydroxyvitamin D3.
A metabolite of vitamin D has been isolated in pure form from incubation of 25-hydroxyvitamin D3 with embryonic chick calvarial cells that had been grown on Cytodex 1 microcarrier beads. The isolation involved dichloromethane extraction of the cells and incubation medium, followed by Sephadex LH-20 column chromatography and high-performance liquid chromatography of the extract. The metabolite was identified as 1 alpha,25-dihydroxyvitamin D3 by means of ultraviolet absorption spectroscopy, mass spectrometry, and sensitivity to oxidation by periodate. This metabolite was not produced by cell-free medium or by cells from embryonic chick liver, skin, or heart. In conclusion, (1) kidney cells are not unique in having 25-hydroxyvitamin D3:1 alpha-hydroxylase activity as previously believed and (2) vitamin D target tissues such as the skeleton may play a direct role in mediating the metabolism of 25-hydroxyvitamin D3 to 1 alpha,25-dihydroxyvitamin D3, a vitamin D metabolite active at those sites.
D000818:Animals; D002112:Calcifediol / Q000378:metabolism*; D002117:Calcitriol / Q000096:biosynthesis*; D002356:Cartilage / Q000378:metabolism*; D002642:Chick Embryo; D002851:Chromatography, High Pressure Liquid; D013058:Mass Spectrometry; D013056:Spectrophotometry, Ultraviolet
D002117:Calcitriol; D002112:Calcifediol