Repeated exposure to the irrigative wastewater in Shijiazhuang induced precancerous lesion associated with cytochrome P450.

In the present study, the carcinogenic effects of the wastewater sample collected from the Dongming Canal in Shijiazhuang city were first detected by the rat medium-term liver bioassay. The experiment contained five groups: a negative control group, a DEN-alone group, 25% wastewater, 50% wastewater, and 100% wastewater. The body weight of rats decreased significantly as the dose increased. Morphologically, we also found that the damage of the hepatic lobule was more serious and the proliferation of liver cells was more obvious as the dose increased. In addition, we observed a significantly increased liver organ coefficient in rat. With the increase in dose, the damage of the hepatocytes was more serious, which was manifested in significantly elevated of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gammaglutamyl transfer peptide enzyme (γ-GT). And, the irrigative wastewater significantly increased GST-p in the liver of rats at both the transcriptional and translational levels dose-dependently, eventually causing precancerous lesions in the liver tissues. CYP1A1 and CYP1B1 expressions in the rat liver cells at the level of transcription and translation were also significantly increased dose-dependently. Our data clearly demonstrated that the irrigative wastewater had a carcinogenetic effect that was associated with CYP1A1 and CYP1B1. The risk of carcinogenic potential to human health might be due to joint action and accumulative effects over a long period of exposure. We can also concluded that the medium-term liver bioassay could be used as an effective method for evaluating the carcinogenicity of complex water mixtures such as irrigative wastewater.