摘要:
为深入探讨汞(Hg)和砷(As)对水生生物的慢性毒性效应,以日本沼虾(Macrobrachium nipponense)为受试生物,以超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、金属硫蛋白(MT)和丙二醛(MDA)为测试分子标志物,研究上覆水中不同浓度Hg和As单一及联合暴露对日本沼虾肝胰腺的氧化损伤及联合作用机制。结果表明:Hg和As单一及联合暴露对4种分子标志物均可产生不同程度的抑制或激活效应。其中,SOD活性均受到抑制,且高浓度As(1 000 μg·L-1)暴露10 d的抑制率最大,高达59.13%;而CAT活性整体被激活,Hg单独暴露下的激活效应要高于As,且在联合暴露组中随着暴露时间的增加呈现出显著的剂量效应关系(P<0.05);MT和MDA含量在Hg和As的暴露下均显著增加(P<0.05)。其中MT对Hg的螯合能力大于As,As单独暴露3 d后MDA变化较小,但10 d后其含量显著增加(P<0.05)。析因方差分析发现,Hg-As对机体的联合作用机制主要表现为协同作用。综合生物标志物响应指数(IBR)评价证实,联合毒性要高于单独毒性,Hg与As在高浓度下联合暴露10 d的IBR值最大,毒性最强,高浓度As单独暴露处理组的毒性次之;同时,机体自身随暴露时间延长对Hg也表现出一定的解毒功能。
Abstract:
To in-depth explore the chronic toxic effects of mercury (Hg) and arsenic (As) on aquatic organisms, oxidative damage and combined toxicity induced by single and joint exposure to Hg and As under different concentrations on river shrimp (Macrobrachium nipponense) were investigated. Superoxide dismutase (SOD), catalase (CAT), metallothionein (MT) and malondialdehyde (MDA) in hepatopancreas of the river shrimps were selected as tested biomarkers. The results showed that single and joint exposure to Hg and As could either inhibit or induce these four biomarkers. While all SOD activities were inhibited, the maximum inhibition rate of 59.13% was observed after 10 day-exposure to high As concentration (1 000 μg·L-1). On the contrary, the CAT was activated as a whole, with higher activation rate at the single Hg treatments and significant dose-effect at the joint exposure groups along the exposure time (P<0.05). MT and MDA levels increased significantly (P<0.05) under the stress of Hg and As, and the chelating ability of MT to Hg was greater than As. MDA level increased slightly after 3-day exposure compared to control group, while showed a significant increase after 10-day exposure (P<0.05). Factorial analysis of variance revealed that the synergistic effects on organism were mainly found during Hg-As joint exposure. Toxicity evaluation based on integrated biomarker response (IBR) also suggested that the toxicity was higher in joint Hg and As exposure than the single exposure. The joint exposure of Hg and As at high concentration after 10 days made the largest contribution to IBR value, indicating the highest toxicity, followed by single As treatment with high concentration. The organism itself also showed a detoxification function to Hg as the extension of exposure time.
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