铜对梨形环棱螺抗氧化酶活性和金属硫蛋白含量的影响

本实验采用暴露重金属的方法，研究了不同浓度硫酸铜（Cu2+ 分别为0、0.005、0.01、0.02、0.05 mg/L）在不同暴露时间（0—14d）下对梨形环棱螺（Bellamya purificata）过氧化氢酶(CAT)、超氧化物歧化酶（SOD）、谷胱甘肽硫转移酶（GST）的活性、还原性谷胱甘肽（GSH）和金属硫蛋白（MT）含量的影响，以探讨Cu2+ 对梨形环棱螺的氧化损伤及其防御作用的机理，并为水环境Cu2+ 污染的早期诊断及生态风险评价提供科学的依据。结果表明：Cu2+对梨形环棱螺肝脏和鳃中CAT、SOD、GST、GSH 和MT 均有明显影响，表现出时间剂量效应。SOD在前4天、CAT在前3天酶活性总体上表现出诱导趋势， GST在前4天酶活性处于诱导状态，随着暴露时间的延长，酶活性下降，到第5天时表现出抑制趋势；随着时间的进一步增长，至14d时， 0.005 mg/L剂量组酶活性维持在正常值附近波动， 0.01 mg/L剂量组酶活性被诱导， 0.02 mg/L剂量组酶活性在肝脏中表现为诱导而在鳃中则被抑制，0.05 mg/L剂量组酶活性被抑制。肝脏和鳃GSH含量的变化与GST相似，在短时间内表现出诱导效应，肝脏GSH在暴露的前5天、鳃GSH在暴露的前4天均处于诱导状态，随着暴露时间的延长，0.005 mg/L剂量组表现出诱导，0.05 mg/L剂量组则受到抑制。MT在整个实验期间均处于诱导状态，各剂量组在0.5d被极显著诱导，随后MT含量出现起伏波动，有上升和下降，至第14天时达到一稳定水平。其中，0.01 mg/L剂量组肝脏的MT在整个实验期间均被极显著地诱导（P <0.01），0.01 mg/L 剂量组的鳃组织MT除第10天外也被极显著诱导（P <0.01）。在暴露14d时，除0.05 mg/L剂量组的肝脏MT外，其余处于极显著诱导状态（P <0.01）。

Effects of copper on antioxidant enzymes activities and metallothionein concentration of Bellamya purificata

An experiment was conducted to study the effects of copper (Cu2+) on the antioxidant enzymes activities of the Bellamya purificat, such as superoxide dismatase (SOD), catalase (CAT), glutathione S-transferase (GST), concentrations of glutathione (GSH) and metallothionein (MT) at different concentrations of Cu2+ (0, 0.005, 0.01, 0.02 and 0.05 mg/L) and different exposure times (0-14d). In order to evaluate the mechanisms of oxidative stress and damnification of Cu2+ on B. purificat, gills and livers were chosen to analyse the biochemical responses, because these organs were brought into contact with environmental pollutants nearly. The results showed that Cu2+ had significant influence on the activities of SOD, CAT, GST and the concentrations of GSH, MT in both gills and livers of B. purificat, and such effects are significantly related to increased exposure time and dosage. The antioxidant enzymes activities in gills and livers could be markedly activated at the beginning days of Cu2+ exposure, such as SOD in 4d, CAT in 3d, and GST in 4d after exposure. The activities of SOD, CAT and GST decreased with the increase of exposure time, till they were inclined to be inhibited in the 5d. On the last day of exposure, the antioxidant enzymes activities in treatments with 0.005mg/L of Cu2+ approached to the normal value, in 0.05 mg/L of Cu2+ were inhibited, and in 0.01mg/L of Cu2+ were induced. The activities of enzymes in treatments with 0.02 mg/L of Cu2+ was activated in liver and reversed in gill. Changes of GSH in livers and gills consisted with that of GST, which was enhanced when Cu2+ exposure began in several days. GSH concentrations in livers were induced after 5-day- Cu2+ exposure, which in gills were induced after 4-day- Cu2+ exposure. GSH contents increased in low dosage (0.005 mg/L) group and decreased in high dosage (0.05 mg/L) group along with continuous Cu2+ exposure. The MTs (concentration of metallothionein) in livers and gills of B. purificata were induced during the whole exposure process. MTs in all groups increased significantly within 12h Cu2+ exposure (p<0.01), decreased slightly later, then increased again, thereafter, reached to a peak value, and then decreased to a stable level on the 14d at last. MT in livers in treatments with 0.01 mg/L of Cu2+ was extremely significantly induced during the whole process (p<0.01), which in gills was also significantly induced (p <0.01) except on the 10d of exposure. On the last day of exposure, the MTs in livers and gills were extremely significant induced (p<0.01) except that of livers in treatments with 0.05 mg/L of Cu2+. These results suggested that all these parameters above were sensitive to the exposure of Cu2+ and could be used as biomarkers to evaluate the aquatic environment Cu2+ pollution and its ecological risk.