| Octylphenol(OP)is one of the degradation products of alkylphenol ethoxylates(APEs).As plasticizers and surfactants,APEs are widely used in industrial and agricultural production,which has caused a large area of water pollution.As a more stable and persistent compound,OP has toxic and estrogenic effects on wild animals by bioaccumulation.It is reported that the number of amphibian populations has been declining in worldwide,environmental chemical pollution is one of the main reasons.In order to explore the toxic effects of OP on amphibian liver,the acute and chronic hydrostatic exposure tests of Rana chensinensis as experimental animal were conducted.Acute exposure test of R.chensinensis exposed to 5×10-5,7.5×10-5,1.63 ×10-4,2.75 × 10-4,3.88 X 10-4 and 5 × 10-4 mol/L OP for 96 hours.During the exposure period,the symptoms of R.chensinensis were observed and the median lethal concentrations(LC50)and safe concentrations(SC)were calculated.Meanwhile,histopathological examination of the dead individual's liver after exposed to OP for 48h.In addition,chronic exposure test of Rana chensinensis exposed to 10-8 10-7 and 10-6 mol/L OP for 10,20 and 30 days.To explore the recovery effect of vitamin C(Vc)on hepatocyte dysfunction induced by OP,adding 30 mg/L Vc to each OP group.Then the livers were dissected and weighed in order to calculate the liver indexs.The microscopic and ultrastructural changes of liver tissue sections were observed by light microscope and transmission electron microscope.What' t more,the apoptosis of liver cells was detected by TUNEL method and the apoptosis indexs were calculated.Another part of the liver tissues were used to measure the activities of superoxide dismutase(SOD),catalase(CAT)and glutathione peroxidase(GPx),the contents of malondialdehyde(MDA)and hydrogen peroxide(H2O2).The main results and conclusions were as follows:1.Results of acute exposure experiment showed that the relationship between regression equation of death probability of R.chensinensis and logarithmic concentration of OP exposure for 24,48,72 and 96h were y=2.598x-0,0394,y=2.2597x+1.004,y=2.2122x+1.5255,y=2.7437x+0.8586;LC50 were 4.10×10-4,2.88×10-4,1.79 ×10-4,1.34 × 104 mol/L;SC was 1.34 ×10-5 mol/L.Histopathologic observation showed that as the concentration of OP increases,some liver tissues of R.chensinensis collapsed,hepatic cord dissociation,blurred contours,cell cytoplasm reduction.These results indicated that high-concentration OP can lead Rana chensinensis to death by acute toxicity,and can cause serious damage to liver cells.2.The results of liver index of R.chensinensis chronic exposed to 10-8,10-7 and 10-6 mol/L OP showed that the liver index were significantly decreased in 10-6 mol/L OP exposed for 10 and 20 days;Exposed for 20 days,the liver index in 10-7 mol/L OP reached the lowest value;And for 30 days,there are no significant difference between the OP treatment group and control group.Compared with 10 and 20 days,the liverindex was significantly decreased in the 10-8 mol/L group at 30 days.The results showed that OP could reduce the weight of the liver in the short term.With prolonged exposure time,it can reduce the weight of R.chensinensis to rebound the liver index.3.Histopathologic findings of liver of R.chensinensis chronic exposure showed that some livers' blood sinus expansion.Exposed for 30 days,some liver tissues accumulated lots of fat,cytoplasmic vacuolization,and even hepatocyte necrosis was observed.Electron microscopic observation showed that some livers' cells have cluster of lipid droplets,endoplasmic reticulum expansion,mitochondria increased in OP treatment.The results showed that OP could induce partial liver tissues and hepatocytes damaged.4.The results of TUNEL showed that apoptotic cells were found in liver tissue of R.chensinensis exposed to OP and control.Apoptotic index(AI)showed that AI was 5.67%in control,34.2%in 10-6 mol/L OP treated for 20 days,which is the highest.In general,there exists dose-effect relationship between OP and AI,time-effect is not obvious.The results indicated that OP could induce hepatocellular apoptosis.5.The results of changes of antioxidant enzyme activities and products showed that the activities of SOD,CAT and GPx decreased first and then increased with the exposure concentration and time,while the contents of H2O2 and MDA were the opposite.The results indicated that OP could cause oxidative stress,but the dose-effect and time-effect were not irregular.In addition,Vc along with OP aggravates oxidative damage in liver of R.chensinensis.In conclusion,OP could lead R.chensinensis to acute poisoning and death in the short term,and the liver tissue structure is seriously damaged.The safe concentration of OP could induce oxidative stress in liver tissue,change the activities of antioxidant enzymes and increase the contents of related products,and even leads to partial hepatocyte apoptosis and some liver tissues damage. |
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