Objective To observe glutathione-S-transferase (GSTs) enzyme activities and the mRNA and protein expressions of GSTA1 gene in the liver of rats exposed to organic extracts (OEs) from drinking water, and to assess the effect of organic extracts from drinking water in the liver injury.
Methods Organic extracts in drinking water were extracted by solidphase extraction method. Fifty SD rats were randomly divided into blank control group, solvent control group (corn oil), and three OEs exposed groups (5, 20, and 80 L/kg body weight per day). The exposure via gavage lasted 12 weeks. Spectrophotometry was used to measure the enzyme activities of GSTs. The mRNA and protein levels of GSTA1 gene were measured by real-time quantitative and Western blot method separately. Liver function was also detected.
Results (1) Compared with the blank control, solvent control, and low dose groups, the enzyme activities of GSTs in the middle dose group(50.66& #177;5.62)U/mg protein and the high dose group(39.80& #177;12.95)U/mg protein both obviously increased (P < 0.05). While compared with the middle dose group, the activities of GSTs in the high dose group significantly decreased (P < 0.05). (2) The mRNA and protein expression levels of GSTA1 in the middle and high dose groups were significantly higher than those in the blank control, solvent control, and low dose groups (P < 0.05). While compared with the middle dose group, the mRNA expression level of GSTA1 in the high dose group significantly decreased (P < 0.05). The results of Western blot showed that with the incease of exposing dose, the expression of GSTA1 protein increased at first then decreased. Compared with the blank control, solvent control, and low dose groups, the GSTA1 protein in the middle and high dose groups elevated significantly (P < 0.05). While compared with the middle dose group, the GSTA1 protein in the high dose group significantly decreased (P < 0.05). (3) Compared with the control group, the augmentation of serum cholinesterase was elevated both in the middle and high dose groups, while serum ALT and AST only elevated significantly in the high dose group (P < 0.05). The total protein and albumin levels decreased significantly in the high dose group (P < 0.05). Positive correlations were identified between GSTA1 protein expression/GSTs activity and liver cholinesterase level (r=0.490 5, r=0.685 2; P < 0.05).
Conclusion Under the reported experimental conditions, exposed to a higher level of organic extracts from drinking water might up-regulate the expression levels of GSTA1 mRNA and protein, induce abnormal changes of GSTs enzyme activities, and result in increased susceptibility to toxic chemicals of rat liver cells.
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