Epidermal cytochrome P-450: immunochemical characterization of isoform induced by topical application of 3-methylcholanthrene to neonatal rat.

To further define the capacity of skin to metabolize various drugs and carcinogens by the cytochrome P-450 (P-450)-dependent monooxygenase, we studied the profile of P-450 isoform(s) in neonatal rat epidermis after application of 3-methylcholanthrene (3-MC) to skin. Highly specific monoclonal antibodies (MAbs) 2-66-3 and 1-7-1 against purified rat liver P-450 isoforms b and c induced by phenobarbital and 3-MC, respectively, were used. After a single topical application of 3-MC to rats aryl hydrocarbon hydroxylase (AHH), 7-ethoxycoumarin-O-deethylase and 7-ethoxyresorufin-O-deethylase activities in epidermal microsomes were induced significantly. Radioimmunoassay of epidermal microsomes from untreated control animals with 35S-labeled MAb-2-66-3 showed significant binding whereas negligible binding with MAb 1-7-1 was observed. On the other hand significant binding was observed with 35S-labeled MAb 1-7-1 with epidermal microsomes prepared from 3-MC-treated animals. Histochemical staining of epidermis from control animals showed no immunoreactivity with either MAb 1-7-1 or MAb 2-66-3 whereas epidermis obtained from 3-MC-treated rats showed significant immunoreactivity with MAb 1-7-1. Western blot analysis of epidermal microsomes prepared from control animals showed no immunoreactivity with either MAb 1-7-1 or 2-66-3 whereas epidermal microsomes prepared from 3-MC-treated animals showed distinct immunoreactivity with MAb 1-7-1. MAb 2-66-3 inhibited AHH and 7-ethoxycoumarin-O-deethylase activity (40-50%) in microsomes prepared from control animals.(ABSTRACT TRUNCATED AT 250 WORDS)