Cultured human keratinocytes cannot metabolize vitamin D3 to 25-hydroxyvitamin D3

AbstractThe metabolism of [3H] vitamin D3 was studied in cultured human keratinocytes (CHK). Intact CHK were incubated for 1, 6, 12, 24 and 48 h with [3H] vitamin D3 and the lipid soluble fractions from the media and cells were extracted by high-performance liquid chromatography (HPLC). Vitamin D3 and its metabolites, 25-OH-D3, 24,25(OH)2D3 were added to the extracts, as markers, prior to HPLC, HPLC analysis of the lipid extracts did not reveal any monohydroxylated metabolites. CHK incubated for one hour with [3H]25-OH-D3 showed a 10±4% conversion to [3H]1,25,(OH)2D3 whereas no conversion to [3H]1,25(OH)2D3 was observed in control CHKs that were boiled prior to incubation with [3H]25-OH-D3. These findings suggest that cultured neonatal keratinocytes are incapable of metabolizing vitamin D3 to 25-OH-D3