Effects Of Phenolic Compounds On Vitellogenin Induction And Enzymes Activities In Goldfish

Recently concerns over environmental endocrine disrupting chemicals (EDCs) especially those with estrogenic activity are heightened. EDCs affect growth and development of individual organisms as well as their offspring, and have potential hazard on ecosystem. Among these EDCs phenolic compounds arouse wide concern because of their ecological significant effects. Current researches bout the estrogenic effects of phenolic compounds usually focus on single chemicals, very few on mixtures.In this paper goldfish was chosen as experimental animal. Estrogenic effects of individual chemicals including nonylphenol (NP), octylphenol (OP), bisphenol A (BPA) and 2,4-dichlorophenol (2,4-DCP) were investigated using vitellogenin induction of male goldfish in vivo. The dose-response relationship was established to evaluate their estrogenic activities. On this basis the effects of mixtures were also studied in two different ratios of equipotent and realistic concentrations. The combined effects of the mixtures were analyzed by the concentration addition model (CA) and four different toxicity indices including toxic unit, additivity index, mixture toxicity index and similarity parameter. The aim of this study was to provide scientific foundation for environmental risk assessment of phenolic compounds and supply reference for environmental quality standars development of these chemicals. This paper also studied the effects on hepatosomatic index (HSI), SOD,CAT and GST activities to discuss the possibility of using this endpoints as biomarkers of phenolic compounds contamination.The results show that NP, OP and BPA can significantly induce the vitellogenin synthesis, so all of them are estrogenic chemicals. The lowest observed effect concentration of NP, OP and BPA is 15,5 and 10μg·L-1 respectively. A nonlinear regression of Weibull function could be applied to the relationship between plasma vitellogenin contents and exposure concentrations. The median effective concentration of E2, NP, OP and BPA for vitellogenin induction was 0.078,255.7, 79.6 and 113.4μg·L-1 respectively, and the relative estrogenic potencies to E2 is 3.05×10-4,9.80×10-4 and 6.88×10-4. The estrogenic potencies of these three phenolic pollutants show an order of OP>BPA>NP.2,4-DCP can also induce vitellogenin systhesis in male goldfish, however the maximum vitellogenin induction is far lower than that of the positive control. The estrogenic potency of 2,4-DCP is much weaker. Vitellogenin induction is also detected in the mixtures of NP, OP and BPA in two different ratios of equipotent and realistic concentration, and dose-response relationship is showed. A nonlinear regression can properly describe the dose-response relationship using Weibull function. The median effective concentrations (EC50) were 149.2 and 168.7μg·L-1 for mixtures in ratio of equipotent of equipotent and realistic concentration respectively. The estrogenic effect of the mixture in ratio of equipotent is a little higher than that in ratio of realistic concentration. The results of different toxicity indices and CA model are similar, and the chemicals acted together in an additive manner, however a little weaker than additive manner at low concentrations and a synergistic manner at high concentrations. The combined effects predicted by CA model are consistent with those observed in the experiments in almost whole range of exposure concentrations, which indicated three chemicals acted in a similar way and the model can be applied to predict the combined effects of the mixtures.All of the four phenolic compounds can significantly induce the hepatosomatic index, and the induction is even more obvious when exposure to the mixtures. The hepatosomatic index may indicate phenolic endocrine disrupting chemicals pollution as a reference index. The effects of individual phenolic compounds on SOD and CAT activities in goldfish liver present the consistent trend:with the exposure concentration increasing the activities are induced initially and then decrease. GST activities can be induced significantly at much higher exposure concentrations. The effects of mixtures of NP, OP and BPA on SOD, CAT and GST activities show obvious dose-response relationship. The activities of the three enzymes increase at low exposure concentrations and then decrease at high concentrations. Exposure to the mixtures SOD and CAT activities show a good correlation, and GST activities are induced more significantly than exposure to individual phenolic compounds. The combination of these three enzymes may indicate phenolic compounds contamination to a certain extent, and have the potential to become their biomarkers.