CYTOCHROME-P-450 CONTENT AND MIXED-FUNCTION OXIDASE ACTIVITY IN MICROSOMES ISOLATED FROM MOUSE SKIN

Abstract

A microsomal fraction, prepared from mouse skin, catalyzed the hydroxylation of benzpyrene and aniline and the deethylation of 7-ethoxycoumarin. Contamination of the preparation by cytochrome oxidase and cytochrome P-420 was determined by spectral analysis. The enzyme activities studied in mouse skin (Swiss-Webster CD-1) did not respond to topical application of 3-MC [3-methylcholanthrene]. Twenty-four hours after topical application of TCDD [2,3,7,8-tetrachlorodibenzo-p-dioxin] to mice, microsomes from skin had 50% greater benzpyrene hydroxylase and 7-ethoxycoumarin deethylase activity, and 4 to 8-fold greater activity of these enzymes was seen after 72 h. Increases in cytochrome P-450 content of skin microsomes could be demonstrated 24 and 72 h after topical TCDD treatment of mice. Cholate treatment (solubilization) of skin microsomes, followed by centrifugation, removed the contaminating cytochrome oxidase. Quantitative and qualitative analyses of cytochrome P-450 difference spectra were made from the solubilized preparations. [Toxicity of organic chemicals in cosmetics, cleaning compounds, medicaments, synthetic fabrics and occupational and polluted environments was of concern.].