A radiometric assay for hepatic epoxide hydrase activity with [7-3H] styrene oxide

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Abstract

[7-3H]styrene oxide is converted to [7-3H]styrene glycol by a hepatic epoxide hydrase. Differential extraction of the incubation medium provides the basis for a rapid, simple method to assay epoxide hydrase activity. Unreacted substrate is first removed by extraction into petroleum ether followed by extraction of the glycol into ethyl acetate for assay by scintillation spectrometry. Enzyme activity is present in liver and kidneys and is localized exclusively in the microsomal fraction. The simplicity of the present assay permits the use of epoxide hydrase a a marker enzyme for microsomal membranes. The specific activity of this enzyme in hepatic microsomes increases during maturation of rats and following pretreatment of rats with phenobarbital or 3-methylcholanthrene.

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A preliminary report of this work has appeared: Federation Proc., 29 (1970) 473.

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