| Three hot topics related to arsenic metabolism were systematically studied in this dissertation, and these include: 1) consumption risk assessment of dry seafood products and Chinese traditional herbs, 2) the difference between normal liver cells and carcinogenic liver cells in arsenic metabolism , and 3) the major existing forms of arsenic-protein during arsenic metabolism in rats,. The contents and major results of the study are outlined as follows:A brief review related to arsenic speciation and arsenic metabolism was made in the first chapter. Three seemingly conflicting characteristics about arsenic metabolism were summarized based on the recent literature survey.In the 2nd chapter, the hyphenated technique of HPLC-ICP-MS was developed for the separation and sequential determination of 6 arsenic species including arsenobetaine (AsB), arsenocholine (AsC), arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV). The method developed was then applied for the speciation analysis of arsenic in a varity of Chinese medicinal herbs. The study indicated that As (â…¤), As (â…¢) were the main chemical species in Chinese medicinal herbs, however, only a limited amount of AsB was found in the animal herbs studied.In the 3rd chapter, a sequential extraction procedure followed by HPLC-ICP-MS analysis was developed for the quantitative analysis of arsenic species in dry seafood products (DSPs). The excellent extraction efficiency could be obtained after three steps extraction (87-115%). A variety of DSPs samples were analyzed using novel extraction method established in the present work. It was observed that the type of arsenic species in the animal DSPs are different from those of the botanic ones. In the animal DSPs, Arsenobetaine (AsB) was the dominate specie, which occupied 62.0-72.7% of the total extractable arsenic in DSPs. Contrary to this, in botanic DSPs, three arsenosugars, DMA-glycerol ribose, DMA-phosphate ribose and DMA-sulfate ribose, identified with HPLC-TOF-MS, were the dominate species. The total content of these 3 species in the samples were in the range of 63.5-92.7%, indicating that the overall toxicity of DSPs were relatively low.Three digestion methods including microwave digestion, cold digestion and obturator digestion were systematically studied in the 4th chapter. The comparative results showed that the microwave digestion was the most efficient method for arsenic determination in samples. Based on the total arsenic determination, arsenic speciation in Chang liver cells (reference material) were performed to identify the arsenic metabolites after their incubation. Two unknown arsenic metabolites, which were speculated as monomethylarsonous acid (MMAIII) and monomethylmonothioarsonic acid (MMTA), were found in the cells. Due to the absence of commercial standards, the MMAIII and MMTA in hepatocytes were tentatively identified and characterized using standard addition method. Furthermore, arsenic metabolites in normal liver cells (Chang liver cells) and carcinogenic liver cells (QGY-7703 cells) were compared by analyzing their arsenic metabolism efficiency. The results indicated that the arsenic metabolism efficiency of carcinogenic liver cells (QGY-7703 cells) was much lower than that of the normal liver cells. Based on the information that both DMAV and MMTA in QGY-7703 cells was undetected, it is speculated that the loss of those two arsenicals was related to the inhabitation of carcinogenic liver cells during arsenic metabolism.In the 5th chapter, arsenic metabolites in rat liver were characterized and speciated using fractional analysis. The rat liver homogenates were separated into 5 fractions based on their different physical and chemical properties and analyzed using HPLC-ICP-MS. The results showed that most of the arsenicals in rat liver exist in free states, which accounts for 42.3-72.8% of the total arsenic. The next was arsenicals binding to non-soluble protein, which accounts for 18.4-33.4%. Arsenicals bond to soluble protein was the least abundant component, which accounts for 8.8-24.3%. Moreover, several kinds of arsenicals could bind to protein in rat liver, and the major component was in the form of dimethylated arsenicals-protein. An investigation of the affinity between arsenicals with different valence and protein suggested that trivalent arsenicals were much easier to bind to protein than those of pentavalent arsenicals. The present study indicated that the dimethylarsinic acid bond to protein (DMAIII-protein) was the major forms of arsenical-protein binding in rat liver. In addition, Arsenicals incubation in vitro showed that mono (di) methylthioarsenicals, including Dimethyldithioarsinic acid (DMDTA) and monomethylmonothioarsonic acid (MMTA) were the common arsenic metabolites in rat liver, which were derived from the metabolism of Monomethylarsonous acid (MMAIII) and Dimethylarsinous acid (DMAIII) in mammals.In the present work, the chemical species and distributions of arsenic in dry seafood products and Chinese traditional herbs were systematically studied. The results might play an important role in well understanding the principle of arsenic toxicity in seafood and Chinese herbs. Moreover, on a basis of the identification and comparison of arsenic metabolites obtained in vivo/vitro, the origination of Thioarsenicals, mechanism of grown inhibition of carcinogenic liver cells after arsenic incubation and major components of arsenic-protein in rat liver were discussed. The above studies and the scientific results might offer useful analytical methodology, scientific information and technical support to the scientists who are working in these areas.
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