| First Author | Masuda S | Year | 2004 |
| Journal | J Steroid Biochem Mol Biol | Volume | 89-90 |
| Issue | 1-5 | Pages | 149-53 |
| PubMed ID | 15225763 | Mgi Jnum | J:91384 |
| Mgi Id | MGI:3046628 | Doi | 10.1016/j.jsbmb.2004.03.094 |
| Citation | Masuda S, et al. (2004) Insights into Vitamin D metabolism using cyp24 over-expression and knockout systems in conjunction with liquid chromatography/mass spectrometry (LC/MS). J Steroid Biochem Mol Biol 89-90:149-53 |
| abstractText | The development of novel gene expression systems for cytochrome P450s (CYPs) together with a revolution in analytical mass spectrometry with the emergence of liquid chromatography/mass spectrometry (LC/MS) has opened the door to answering some long-standing questions in Vitamin D metabolism. Our studies focused on: (1) elucidating the role of CYP24 in 25-OH-D(3) and 1alpha,25-(OH)(2)D(3) metabolism; (2) exploring how DBP influences this process; (3) measuring 25-OH-D(3) metabolism in CYP24-knockout (CYP24-XO) cells and; (4) comparing 1alpha-OH-D(2) metabolism in the CYP24-XO mouse in vivo and in vitro. Methodology employed CYP24 over-expression and knockout systems in conjunction with state-of-the-art analytical LC/MS, diode array, and radioisotopic detection methods. We found that CYP24 metabolizes 25-OH-D(3) and 1alpha,25-(OH)(2)D(3) at similar rates in vitro, but that for 25-OH-D(3) but not 1alpha,25-(OH)(2)D(3), this rate is strongly influenced by the concentration of DBP. Unlike their wild type littermates, the administration of 25-OH-D(3) to CYP24-XO mice results in no measurable 24,25-(OH)(2)D(3) production. When neonatal murine keratinocytes are prepared from wild type and CYP24-XO mice there was no measurable production of 24,25-(OH)(2)D(3) or 1alpha,24,25-(OH)(2)D(3) in CYP24-XO mice. Similar experiments using the same wild type and CYP24-XO animals and cells and [Formula: see text] 1alpha-OH-D(2) resulted in the apparent paradox that the Vitamin D prodrug was 25-hydroxylated in vivo but 24-hydroxylated in vitro. |
