Gene Expression of Cytochrome P450 1A in Hybrid Catfish (Clarias gariepinus × Clarias macrocephalus) Exposed to Chlorpyrifos or Carbaryl Insecticides

Cytochrome P450 1A (CYP450 1A) induction is used widely as a biomarker when assessing exposure to contaminants in environmental systems including pesticides. The effect of chlorpyrifos and carbaryl on CYP450 1A induction was assessed both by measurements of the induction of the EROD activity and the CYP450 1A gene expression in hybrid catfish (Clarius gariepinus x Clarius macrocepharus). Fish were treated with several concentrations of chlorpyrifos (0.43, 4.3 or 43 μM), or carbaryl (1.19, 11.9 or 119 μM) for 24 or 48 h. The livers were then assayed for changes. Chlorpyrifos and carbaryl at all concentrations slightly increased the levels of EROD activity after 24 and 48 h and increased gene expression of CYP450 1A mRNA in dose-dependently. Exposure to chlorpyrifos and carbaryl at high concentrations resulted in significant elevation of CYP450 1A gene expression in comparison to control fish (P < 0.05) at both time intervals. These results showed that the responses of CYP450 1A were more pronounced in gene expression analysis than in EROD assay. This suggests that the induction of CYP450 1A at the gene level was more sensitive than at the protein level. The induction of CYP450 1A following chlorpyrifos and carbaryl exposure indicates the possible use of CYP450 1A as a biomarker for detecting effects of these pesticides in hybrid catfish.