The hepatic microsomal mixed-function oxygenase (MFO) system ofAlligator mississippiensis: induction by 3-methylcholanthrene (MC)

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Abstract
1. Pretreatment of alligators i.p. with 3-methylcholanthrene (MC) resulted in a 1.6-fold increase (PN-demethylase and 7-ethoxycoumarin O-deethylase were unaffected by MC treatment. 4. The O-dealkylation (OD) of a series of alkoxyresorufins (ethoxyresorufin (ER), methoxyresorufin (MR), benzyloxyresorufin (BR), and pentoxyresorufin (PR)) was investigated. MC treatment resulted in a significant (P<0.001) increase in turnover number of EROD, MROD, and BROD over control values. The turnover number of PROD was unaltered by MC treatment. 5. Western blots showed that control alligator microsomes contain a protein band of lower mol. wt. than either rat cytochrome P-450c (P450 IA1) or P-450d (P450 IA2), which was recognized by antibodies to both P-450c and P-450d but preferentially by that against P-450c. This protein band was induced 3-4-fold by MC. MC treatment induced a second protein band in alligator microsomes of the same mol. wt. as rat P-450d, recognized preferentially by antibodies to rat cytochrome P-450d. 6. These results illustrate that the alligator mixed-function oxidase (MFO) system responds to MC in a similar manner as described in mammals, i.e. induction in P-450 content, increases in specific MFO activities, and the apparent expression of different P-450 isoenzymes.