| In order to evaluate the toxicological and endocrine disrupting mechanism of bisphenol A (BPA) in aquatic animals, the acute toxicity, the histological damage, and endocrine disruption of BPA on zebrafish were studied. BPA had acute toxicity on zebrafish. After exposure to BPA, the liver and gonad were damaged in various extent. BPA had endocrine disrupting effects on zebrafish.1. Acute toxicity of BPA on zebrafishAfter 6 h exposure to BPA of high concentration group, zebrafish swam slowly down, lost balance, sank to the bottom, then breath became weak. Death zabrafish were observed after 12h exposure to BPA in the high concentration group. The 96 h LC50 of BPA was 6.3 mg·L-1. Zebrafish are sensitive to BPA. The safe concentration was 0.63 mg·L-1.2. Liver damage and oxidative stress of BPA on zebrafishIn order to understand the toxical effects and mechanism of BPA on zebrafish, the histological damage and the indicators regarding to oxidative stress relative such as activities of superoxide dismutase (SOD) and GSH-Px (GPX) in hepatopancreas were examined at intervals 0,6,12 , 24 and 48 h after being treated with BPA with spectrophotometry. The liver damage was observed in concentration-dependent way. In the group of BPA 0.2 mg·L-1, the livers were slightly damaged. In the group of BPA 2 mg·L-1, the livers were damaged, hepatocyte cloudy swelling and pyknosis were appearing. In the group of BPA 6.1 mg·L-1 , the livers were badly damaged with cell vacuolization, necrosis, and cavity. After 6 h treated with BPA,SOD level was higher in all treated group than in the control group. The group of 6.1 mg·L-1 was significantly higher than that in the control group (P < 0. 05). After 12 h treated with BPA,there wasn't diffidence in SOD level between the treated group and control groups. After 24 h treated with BPA,SOD level was lower in all treated groups than in the control group. In the 48 hours exposure to BPA, the activities of GPX in the group of BPA 0.1 and 0.6 mg·L-1 showed no signifcant difference during the treatments. The activities of GPX in the group of BPA 6 mg·L-1 were induced during the treatments. The results indicated that liver was the target organ of BPA.3. Zebrafish gonad damage by BPAIn order to evaluate zebrafish gonad damages by BPA, the zabrafishes were treated with BPA for 96h. In high BPA group (6.1 mg·L-1), the testis structure was damaged, and the atresia rate of ovarian follicle was 35%. In the group of 0.2 mg BPA·L-1, the livers were slightly damaged, gonad had no morphological change, the rate of gametes number in late phaseⅢto that in phaseⅣin ovary increased a little, and oocyte size increased significantly (P<0.05). In the group of 2 mg BPA·L-1 , the rate of gametes number in late phaseⅢto that in phaseⅣin ovary increased slightly. In the group of 6.1 mg BPA·L-1, the testis structure was subject to certain damage, the pyknotic nuclei were also observed, and atresia of overian follicle increased significantly. In 2 mg BPA·L-1 group, the number of sperm head per gram of testies increased at 12h exposure and decreased at 24 and 48h exposure. In 2 mg BPA·L-1 group, the number of sperm head per gram of testies increased at 12h and 24h exposure and decreased at 48h. In 8 mg BPA·L-1 group, the number of sperm head per gram of testies was significantly higher than the control group.Testicular sperm head count results were consistent with the testis histological results.4. BPA endocrine disrupting influence on the zebrafishIn order to better understand the BPA endocrine disrupting influence on zebrafish and its possible mechanism, the expression of Esr1 (ERα), AhR2 and VTG mRNA in the male zebrafish livers were detected following the exposure to bisphenol A (BPA). At different exposure time, the total liver RNA were extracted and OD value were determined with ultraviolet spectrophotometer. The male zebrafish liver RNA was analyzed with the quantity PCR. The results showed that BPA had endocrine disrupting effect on male zebrafish liver: BPA increased the expression of Esr1 and VTG1mRNA in male zebrafish liver, also increased the expression of AhR2 a little. After 12 h treated with BPA the Esr1 and VTG1 mRNA level significantly increased (P<0.05) and still remained high level at 24h. Esr1 and VTG1 mRNA level was significantly different between the treated groups and the control group (P<0.05). Esr1 mRNA level continued to rise at 48h. After 72 h treated with BPA,Esr1 and VTG1 mRNA level was lower than at 12, 24 and 48h exposure. Esr1 and VTG1 mRNA level at 72h was a littlel high than in the control group(P>0.05). During the experiment of 96h exposure, AhR2 mRNA level rose at 48h. Esr1 and VTG1 mRNA levels changing showed the similar way during the treatments. The results showed that the BPA's endocrine disrupting in zebrafish has a number of ways. |
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