Assay of cholesterol 7a-hydroxylase in liver microsomes

Assay of the enzyme activity is complicated by the fact that 7a-hydroxylation of cholesterol also may occur due to auto-oxidation or secondary to lipid preoxidation. In addition it is difficult to equilibrate exogenous cholesterol with endogenous microsomal cholesterol. 

In the first studies on 7a-hydroxylation, the microsomal fraction together with the 

Balasubramaniam and co-workers have proposed the term substrate pool for 

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