菲律宾蛤仔对三价和五价无机砷的富集转化规律

摘要

砷是具有类金属特性的污染物,不同赋存形态的砷毒性差异极大,海洋贝类由于其生活习性易于富集高浓度的砷,本研究以菲律宾蛤仔(Ruditapes philippinarum)为对象,探讨其在亚砷酸盐(arsenite,AsⅢ)和砷酸盐(arsenate,AsV)暴露14天后的生物富集和转化规律.结果表明,菲律宾蛤仔对砷的积累量随海水中无机砷浓度的升高而逐渐增加.但菲律宾蛤仔鳃组织对砷的生物利用度很低,10ug/L暴露组菲律宾蛤仔鳃组织对砷的积累量与对照组相比无显著差异.菲律宾蛤仔对三价砷的生物利用度高于五价砷,且砷更易于在菲律宾蛤仔肝胰腺中积累.菲律宾蛤仔组织中无机砷转化过程主要包括As(Ⅲ)氧化,As (V)还原和甲基转化.在对照组和各暴露组有机砷砷甜菜碱(AsB)和二甲基胂酸(dimethylarsinic acid,DMA)是主要赋存形态,一甲基胂酸(monomethylarsonic acid,MMA)在100ug/LAs (V)暴露处理后含量显著下降,表明在无机砷的限速转化反应中MMA可以较快地代谢或转化为其他赋存形态.无机砷在菲律宾蛤仔鳃组织中主要转化为DMA,肝胰腺中主要转化为AsB.以上研究结果为阐明菲律宾蛤仔的生物富集和转化机制提供了重要依据,同时也可为贝类安全养殖和食用提供一定理论依据.%Arsenic (As) is a ubiquitous toxic metalloid,and its toxicity depends greatly on its chemical speciation.Marine mollusks are apt to bioaccumulation of high arsenic contents because of their living habits.In this study,the bioaccumulation and biotransformation of the clam Ruditapes philippinarum were investigated after waterborne exposure to arsenite (As (Ⅲ)) or arsenate (As (V)) for 14 days.The results showed that arsenic uptake increased with increasing arsenic concentration in the seawater,while gills of R.philippinarum showed the limited ability to bioaccumulate inorganic arsenic from seawater,with no significant difference compared with control group following waterbone 10 μg/L As (Ⅲ) and As (V) exposure for 14 days.The bioavailability of As (Ⅲ) was slightly higher than that of As (V) to R.philippinarum,and arsenic was easier to be accumulated in digestive glands.The results demonstrated the As biotransformation in the clams included As (V) reduction,As (Ⅲ) oxidation,and methylation.Arsenobetaine (AsB) and dimethylarsinic acid (DMA) was the major arsenic speciation in all treatments,while monomethylarsonic acid (MMA) contents decreased significantly after exposure,indicating that MMA can be quickly metabolized or converted into other arsenic speciation in the rate-limiting conversion reaction of inorganic arsenic.Inorganic arsenic in gills was mainly converted to DMA,but AsB in digestive glands,indicating the different transformation efficiency in different tissues.In summary,the results provided an important basis for elucidating the arsenic bioaccumulation and biotransformation mechanism in R.philippinarum and provided theoretical basis for shellfish breeding and food safety.