Integrated biomarkers in wild crucian carp for early warning of water quality in Hun River, North China.

Metabolizing enzymes play important roles in the detoxification of various pollutants in aquatic organisms, thereby they can also be used to provide early-warning signals of environmental risks. Real-time quantitative reverse-transcription polymerase chain reaction assays were developed to quantify cytochrome P450 1A (CYP1A), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and glutathione-S-transferase (GST) in crucian carp (Carassius auratus). The methods were then used to detect the respective mRNA expression levels in liver tissue in wild crucian carp from the Hun River, North China. CYP1A mRNA expression was significantly up-regulated in fish from stations S5, S6, and S8 (p < 0.05). SOD mRNA expression was significantly down-regulated in downstream areas relative to fish from upstream sites (p < 0.05); GPx and CAT mRNA expression levels were also down-regulated at S9 (p < 0.05). In contrast, GST mRNA expression showed no obvious change between fish collected from up- or downstream areas of the river. Finally, an integrated biomarker response was used to evaluate the integrated impact of pollutants in the Hun River and allow better comprehension of the real toxicological risk of these investigated sites.