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4β-hydroxy Cholesterol-d7 is intended for use as an internal standard for the quantification of 4β-hydroxy cholesterol by GC- or LC-MS. 4β-hydroxy Cholesterol is a major oxysterol cholesterol metabolite and a precursor in the synthesis of bile acids that is found in human circulation.1 It is formed from cholesterol by the cytochrome P450 (CYP) isoforms CYP3A4 and CYP3A5.1 4β-hydroxy Cholesterol has an unusually long half-life in plasma (~60 hours) as a result of slow elimination, particularly due to a slow rate of 7α-hydroxylation, which is the rate-limiting step for further conversion into bile acids.

1.Dicfalusy, U., Kanebratt, K.P., Bredberg, E., et al.4β-Hydroxycholesterol as an endogenous marker for CYP3A4/5 activity. Stability and half-life of elimination after induction with rifampicinBr. J. Clin. Pharmacol.67(1)38-43(2009)

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