Effects Of 1,2,4-TCB On The Cellular And Molecular Toxic Mechanism Of Eisenia Fetida

With the rapid development of human society, the effects of persistent organic pollutants(POPs) on environmental stress have been growing interesting, because of excessive utilization and incorrect discharge of POPs in recent decades. Soil is one of important natural resources for human, and earthworm is one of important components and largest groups which played important roles in the soil ecosystem. Earthworm has become an important bioindicator and ecotoxicological diagnosis organism to reflect soil pollution. Toxic effects of 1,2,4-TCB to Eisenia fetida in natural soil tests were studied at individual, organism, cell and gene level.The results showed that effects of 1,2,4-TCB were concentration dependent and the survival rate decreased with increasing 1,2,4-TCB concentration. The median lethal concentration(LC50)values were 945±175 and 890±169 mg/kg, respectively, for days 7 and 14 in the natural soil test, confidence limits (95%) were 727.093 ~ 1076.900 and 680.215 ~ 1018.429 mg/kg by probability regression analysis. Significant effects were found when the earthworms were exposed to different concentration of 1,2,4-TCB. ANOVA analysis suggested that duration and concentration had a significant effect on growth inhibition rates, but no significant interaction between these parameters was found.SOD activities were significantly activated when the earthworms were exposed to 100 mg/kg 1,2,4-TCB. On the whole, SOD activities were significantly activated at medium concentration of 1,2,4-TCB, and SOD activity decreased at high concentration. Both exposure time and 1,2,4-TCB dosage had significant effects to SOD activities, and there were significant interaction between them. AChE activitities were inhibited significantly at 400 mg/kg 1,2,4-TCB. Both exposure time and 1,2,4-TCB dosage had significant effects to AChE activities, but no significant interaction was found between them.There were no significant effects on SOD activities at low concentrations of 1,2,4-TCB and Phe combined treatment, and SOD activities were significantly activated at medium concentrations and inhibited relatively at high concentrations. AChE activities showed no significant effects at low concentrations of 1,2,4-TCB and Phe combined treatment and significant inhibition at high concentrations.Microstructure and ultrastructure of the skin and intestinal epithelium in earthworm was examined at 14-day exposure of 1,2,4-TCB. The results showed that structure of the skin and intestinal epithelium changed at different concentrations and damaged seriously at 400 mg/kg 1,2,4-TCB. Ultrastructures showed that mucous cells in the skin and mitochondrials in intestinal epithelial cells changed differently at different concentrations of 1,2,4-TCB.The express of l-rRNA and Hsp 90 mRNA were analysed by real-time quantitative RT-PCR when earthworms were exposed to different concentrations of 1,2,4-TCB for 14 days. The results showed that the express of Hsp 90 mRNA was changed dependent on the concentrations of 1,2,4-TCB. The express of l-rRNA was significantly inhibited, the inhibition rate depended on 1,2,4-TCB concentration.