Notes: 3β-hydroxy-7-oxo-5-Cholestenoic Acid-d3 is intended for use as an internal standard for the quantification of 3β-hydroxy-7-oxo-5-cholestenoic acid by GC- or LC-MS. 3β-hydroxy-7-oxo-5-Cholestenoic acid is a metabolite of the oxysterol 7-keto cholesterol (Item No. 16339).{62928} It is formed from 7-keto cholesterol by the cytochrome P450 (CYP) isoform CYP27A1. Plasma levels of 3β-hydroxy-7-oxo-5-cholestenoic acid are increased in a rat model of liver injury induced by carbon tetrachloride.{62927}