Effects Of Cadmium On Antioxidatant And Immunologic Defence Of Digestive Gland And Gill In The Freshwater Mussel (Anodonta Woodiana)

The freshwater mussel?Anodonta woodiana?was chosen for researching in laboratory for this study.The study was divided into two parts:1.Cadmium exposure and eliminated The freshwater mussels were exposed to waterborne cadmium(Cd²⁺,0,0.5,5 and 50 mg/L)for 14 days and were sampled at 1,4,7 and 14 days.Then the Cd-exposed mussels were removed to clean water for a further 14 days and mussels were sampled at 1,4,7 and 14 days during the recovery period.The accumulation of Cd²⁺,the enzymes activities of?superoxide dismutase?SOD?,acid phosphatase?ACP?and alkaline phosphatase?AKP??and the content of malondialdehyde?MDA?were measured.Results showed that:?1?In the digestive gland,the level of Cd²⁺ of mussels,which were exposed to 5 mg/L and 50 mg/L Cd²⁺,showed a significant?P<0.01?enhancement compared to controls during the period of Cd²⁺ exposure.At the period of recovery,Cd²⁺ accumulation of the two treatments showed tiny decreases,but still higher than controls.The SOD activity was significantly?P<0.01?inhibited during the period of exposure and the first day of recovery.The activity of SOD exhibited a pattern of induction-inhibition in all groups.The ACP activity was significantly?P<0.01?induced on 4 d and 7 d during the period of Cd²⁺ exposure,but the activity displayed irregular changes during the recovery period.During the period of exposure,the AKP activty was significantly?P<0.01?increased in the 5 mg/L and 50 mg/L Cd²⁺ groups on 4 d and 7 d but was significantly?P<0.01?inhibited in the 0.5 mg/L and 50 mg/L Cd²⁺groups on the 14 d.The AKP activity was significantly?P<0.01?decreased on 4 d and 14 d during the period of recovery.The content of MDA was significantly?P<0.01?increased during the period of Cd²⁺exposure,and decreased during the recovery period but still higher than controls.?2?In the gill,the content of cadmium in tissue was increased in Cd²⁺ exposure and decreased in recovery.The content of cadmium in 5 mg/L and 50mg/L groups were significantly higher than that of control.The activity of SOD was significantly?P<0.01?induced during the early Cd²⁺ experosure while the siginificantly?P<0.05?induction was only found in 50 mg/L group on 14 d.The SOD activity of all groups was significantly?P<0.01?increased on 4 d but the significantly?P<0.05?inhibited was found in the 0.5 mg/L group after that day.ACP activity was significantly?P<0.01?inhibited in 0.5 mg/L and 5 mg/L groups on first day while the activity of 0.5 mg/L group was significantly?P<0.05?induced.The activities were significantly inhibited?P<0.01?in all groups on 7 d and the notably?P<0.05?induction was only found in 50 mg/L group on 14 d.During the period of recovery,the activities of ACP were distinctly inhibited and all groups were inhibited from 7 d in the recovery period.During the period of Cd²⁺ exposure,AKP activity was significantly?P<0.01?induced on 4 d but the irregular changes showed in other days.During the recovery,AKP activity was reduced and the significant changes were found in 0.5 mg/L and 50mg/L groups.The content of MDA was significantly increased during Cd²⁺ exposure period and decreased in early recovery period,but increased again at the end of recovery.2.Cadmium and Aeromonas hydrophila association The mussels were exposed to cadmium and challenged by bacteria?Aeromonas hydrophila?for determining the changes of biochemical parameters.The freshwater mussels were exposed to waterborne cadmium?0,0.5,5 and 50 mg/L?for 14 days.Thereafter,different treatments were performed for 24 h?I:no treatment;II:injected into 100?l PBS;?:microbial challenge with 100?l injections of bacterial?.The antioxidative enzymes?superoxide dismutase?SOD?,catalase?CAT?,glutathione peroxidase?GPx?,glutathione S-transferase?GST??,phosphatase?acid phosphatase?ACP?and alkaline phosphatase?AKP??and lipid peroxide?MDA?were determined in the digestive gland.Results showed that:?1?The Cd-exposed mussel response to the bacteria byenzymes activities changed.The SOD activity was inhibited but GPx activity was induced in all concentrations.The activity of CAT was significant induced in the groups of 5 mg/L and 50 mg/L and GPx activity was induced in the groups of 0.5 mg/L and 50 mg/L.ACP activity showed no significant change and AKP activity was significant inhibited in 5 mg/L group.The content of MDA was reduced in 5 mg/L group.?2?The Cd-exposed mussel response to the bacteria by enzymes activities changed.The GST activity was inhibited in all concentrations,and the activities of SOD?CAT?GPx and ACP were inhibited in the groups of 5 mg/L and 50 mg/L.But AKP activity was inhibited in the groups of 0.5 mg/L and 5 mg/L,and the content of MDA showed no change in all concentrations.Conclusion:?1?The antioxidative enzymes were interferenced and the phosphatase metabolic disorders in the Cd-exposure mussels.These changes indicated that the immune system of mussel was disturbed by heavy metal.The clean-water treatment did not make it recover from damage.?2?The antioxidative enzymes were interferenced and the phosphatase metabolic disorders in the Cd-exposure mussels but the bacteria can also influence the enzymes.That result showed that antioxidative enzymes contributed to antibiosis and phosphatase was tissue-specific.The gill of mussel was a sensitive organ.