title: Metabolism of 1alpha,25-dihydroxyvitamin D(3) and its C-3 epimer 1alpha,25-dihydroxy-3-epi-vitamin D(3) in neonatal human keratinocytes.
abstract: We previously reported that 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] is metabolized into 1alpha,25-dihydroxy-3-epi-vitamin D(3) [1alpha,25(OH)(2)-3-epi-D(3)] in primary cultures of neonatal human keratinocytes. We now report that 1alpha,25(OH)(2)-3-epi-D(3) itself is further metabolized in human keratinocytes into several polar metabolites. One of the polar metabolite was unequivocally identified as 1alpha,23,25-trihydroxy-3-epi-vitamin D(3) by mass spectrometry and its sensitivity to sodium periodate. Three of the polar metabolites were identified as 1alpha,24,25-trihydroxy-3-epi-vitamin D(3), 1alpha,25-dihydroxy-24-oxo-3-epi-vitamin D(3) and 1alpha,23,25-trihydroxy-24-oxo-3-epi-vitamin D(3) by comigration with authentic standards on both straight and reverse phase HPLC systems. In addition to the polar metabolites, 1alpha,25(OH)(2)-3-epi-D(3) was also metabolized into two less polar metabolites. A possible structure of either 1alphaOH-3-epi-D(3)-20,25-cyclic ether or 1alphaOH-3-epi-D(3)-24,25-epoxide was assigned to one of the less polar metabolites through mass spectrometry. Thus, we indicate for the first time that 1alpha,25(OH)(2)-3-epi-D(3) is metabolized in neonatal human keratinocytes not only via the same C-24 and C-23 oxidation pathways like its parent, 1alpha,25(OH)(2)D(3); but also is metabolized into a less polar metabolite via a pathway that is unique to 1alpha,25(OH)(2)-3-epi-D(3).
authors.affiliation: Department of Pediatrics, Women and Infants' Hospital of Rhode Island, Brown University School of Medicine, Providence, RI 02905, USA. sreddy@wihri.org
authors.forename: G S
authors.initials: GS
authors.lastname: Reddy
authors.forename: K R
authors.initials: KR
authors.lastname: Muralidharan
authors.forename: W H
authors.initials: WH
authors.lastname: Okamura
authors.forename: K Y
authors.initials: KY
authors.lastname: Tserng
authors.forename: J A
authors.initials: JA
authors.lastname: McLane
mesh_terms: D002117:Calcitriol / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism*; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007231:Infant, Newborn; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D015394:Molecular Structure; D014807:Vitamin D / Q000031:analogs & derivatives / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: C118756:dihydroxy-vitamin D3; D014807:Vitamin D; D002117:Calcitriol