Bioaccumulation and the expression of hepatic cytochrome P450 genes in marine medaka (Oryzias melastigma) exposed to difenoconazole

This study was conducted to assess the effects of difenoconazole (DFZ), a triazole fungicide, on the hepatic biotransformation system and its bioaccumulation in marine medaka (Oryzias melastigma). Fish were exposed to DFZ (1, 10, 100, 1000 ng/L) for 180 days. The results showed that: (1) The mRNA levels of hepatic CYP1A1, CYP1B, CYP1C1, CYP27B and CYP3A40 were up-regulated, but those of CYP3A38 and CYP27A1 were down-regulated. (2) The activity of ethoxyresorufin-O-deethylase (EROD) and the content of reduced glutathione (GSH) in the liver were increased in the DFZ-treated groups, and glutathione S-transferase (GST) activity was increased in the 100 and 1000 ng/L groups. (3) DFZ was accumulated in the muscle and the biological concentration factors in the 10, 100, and 1000 ng/L groups were respectively 149, 81 and 25. These results suggested that long-term exposure to DFZ at low concentrations would result in a bioaccumulation of this compound and disturb the biotransformation system.