Differential Induction of Hepatic Cytochrome P450 Isoforms in Clarias batrachus Exposed to Ethion and Dicofol

Pesticides and their byproducts are commonly encountered by aquatic organisms, such as fish. Cytochrome P450 (CYP 450) monooxygenases are widely distributed, multifunctional enzymes essential for the detoxification or activation of pesticides and serve as a biomarker for evaluating the aquatic environment’s health. The current study examined the effects of organophosphate (ethion) and organochlorine (dicofol) class of pesticides on CYP 450 enzymes in Clarias batrachus after treatment for 5, 10 and 15 days at a 1/3 sub-lethal dosage of the laboratory calculated 96 hour LC50 value. Liver somatic index (LSI), microsomal protein, total CYP 450 content and CYP1A, CYP2B, CYP2E1, CYP3A4 facilitated 7-ethoxyresorufin O-deethylase, N, N- dimethylaniline demethylase, aniline hydroxylase and erythromycin N-demethylase activities in hepatic microsomes were studied. In the pesticide-treated groups, there was a considerable increase in LSI, microsomal protein, and total CYP 450 content. When compared to their respective control groups, the ethion and dicofol-treated groups showed a significant induction (p<0.05, p<0.01) in CYP1A and CYP3A4 activity. No responses were shown by CYP2E1 activity in either of the treatment groups, but only the ethion-treated group showed a substantial induction in CYP2B activity (p<0.05). CYP1A mediated activity was the most pronounced of all the activities.