Inhibition of gizzard shade (Dorosoma cepedianum) P4501A activity by in vivo and in vitro administration of clotrimazole
- Miami Univ., Oxford, OH (United States). Dept. of Zoology
The ability of the 1-substituted imidazole agent clotrimazole to inhibit in vivo and in vitro hepatic microsomal ethoxyresorufin O-deethylase (EROD) activity was investigated using gizzard shad (Dorosoma cepedianum) pre-treated with clotrimazole and then given waterborne exposures of benzo[a]pyrene (BaP). Gizzard shad pre-treated with 50 mg clotrimazole/kg and then exposed for 1 or 3 d to BaP (0.86 {micro}g/L) had significantly lower hepatic EROD activity compared to fish that were exposed to BaP alone. Following 1 and 3 d of BaP exposure, groups pre-treated with clotrimazole had 7% and 28% of the EROD activity respectively relative to groups exposed to BaP alone. In addition, there was 8x and 11x more parent BaP in whole-fish extracts from gizzard shad pre-treated with clotrimazole after 1 and 3 d of BaP exposure, respectively, compared to fish exposed to BaP alone. Clotrimazole produced a ``type 11`` binding spectral complex with BaP-treated microsomes and was an effective in vitro inhibitor of EROD activity in micromolar concentrations. The IC{sub 50} for EROD activity was 0.57 {micro}M clotrimazole. The mechanism of inhibition by clotrimazole was determined to be noncompetitive (mixed type) using kinetics experiments. Noncompetitive inhibition of monooxygenase activity is believed to arise from the interaction created via the non-bonded electrons of the nitrogen in the imidazole ring with the name moiety of cytochrome P450, resulting in inhibition of enzymatic activity. The high inhibitory potency of clotrimazole on P4501A catalyzed reactions may prove valuable for its use as a probe in determining whether chemical toxicity is manifested through a cytochrome P450-mediated pathway.
- OSTI ID:
- 392321
- Report Number(s):
- CONF-9511137--; ISBN 1-880611-03-1
- Country of Publication:
- United States
- Language:
- English
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