Ryoji Sawamura

Induction of DNA damage by dimethylarsine, a metabolite of inorganic arsenics, is for the major part likely due to its peroxyl radical

To reveal the mechanisms of previously reported lung-specific DNA strand scissions in murine after oral administration of dimethylarsinic acid (DMAA), a main metabolite of inorganic arsenics in mammals, the ultimate substance causing DNA lesion was investigated using dimethylarsine which was a further metabolite of DMAA. The alkaline elution assay using 3H-labeled DNA showed that a major portion of the strand breaks was not suppressed by SOD and catalase, suggesting an ultimate substance other than active oxygen participated in the DNA damage. By ESR analysis, a radical estimated to be (CH3)2AsOO. was detected as a reaction product of dimethylarsine and molecular oxygen. This peroxyl radical, rather than active oxygen, was assumed to play a major role in DNA damage.

Cellular response to oxidative damage in lung induced by the administration of dimethylarsinic acid, a major metabolite of inorganic arsenics, in mice

Oral administration of dimethylarsinic acid (DMAA), a major metabolite of inorganic arsenics, induces DNA damage in the mouse and rat lung due to both active oxygens and dimethylarsenic peroxyl radical produced in the metabolism of DMAA. Our paper describes the cellular response to DMAA in the mouse lung. In male ICR mice given a single po dose (1500 mg/kg) of DMAA-Na, the activities of mitochondrial superoxide dismutase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase significantly increased at 6 hr or longer after dosing, while cytosolic superoxide dismutase and catalase did not. With regard to cellular sulfhydryls after DMAA dosing, levels of reduced glutathione and nonprotein sulfhydryl decreased, while mixed disulfides significantly increased. Further, NADPH markedly decreased at 6-9 hr after DMAA dosing. These cellular variations suggest that the mouse pulmonary cell produced active oxygens, i.e., superoxide anion radical, hydrogen peroxide, and subsequent radicals in the metabolism of DMAA and that these and also the dimethylarsenic peroxyl radical were responsible for pulmonary DNA damage.

Dimethylated arsenics induce DNA strand breaks in lung via the production of active oxygen in mice

In order to study the genotoxicity of arsenics, we focused our attention on dimethylarsinic acid (DMAA) which was a main metabolite of inorganic arsenics in mammals. ICR mice were orally administered DMAA-Na (1500mg/kg). DNA single-strand breaks occurred specifically in lung at 12h after administration. An in vitro experiment indicated that the breaks were not caused directly by DMAA but by dimethylarsine, a further metabolite of DMAA. Furthermore, the dimethylarsine-induced breaks were diminished by the addition of SOD and catalase, suggesting that active oxygen produced by dimethylarsine was involved in the induction of DNA damage.

DNA strand breaks in mammalian tissues induced by methylarsenics.

DNA damage induced by administration of dimethylarsinic acid (DMAA) to rats and mice was investigated. At 12 h after administration of DMAA, DNA single-strand breaks were induced markedly in lung. The majority of dimethylarsine, one of the main metabolites, in the expired air was excreted within 6–18 h after administration of DMAA to rats. In vitro experiments using nuclei isolated from lung of mice indicated that DNA strand breaks were caused by dimethylarsine. Furthermore, the strand breaks after exposure to dimethylarsine were reduced in the presence of catalase and/or superoxide dismutase. These results strongly suggest that the strand breaks are induced not by dimethylarsine itself but by active oxygen, e.g., O2− and ·OH, produced both by dimethylarsine and molecular oxygen. When DNA was exposed to dimethylarsine, thiobarbituric acid (TBA)-reactive intermediates andcis-thymine glycol were produced. Dimethylarsine appears to induce DNA damage by the mechanism similar to the damage produced by ionizing radiation.

Differences between freshwater and seawater killifish (Oryzias latipes) in the accumulation and elimination of pentachlorophenol

Freshwater and seawater acclimated (FWA and SWA) killifish (Oryzias latipes) were exposed to pentachlorophenol (PCP) for 3–10 days. Uptake and clearance rates of FWA and SWA killifish were determined. The estimated bioaccumulation factors (BCF) of PCP for FWA and SWA killifish were 1680 and 370, respectively. The smaller uptake rate and faster clearance rate resulted in the lower BCF for SWA killifish. Fresh- and seawater killifish excreted the PCP metabolites, the glucuronide and sulfate conjugates of PCP; the major metabolite of freshwater killifish was PCP sulfate; for seawater acclimated fish, it was PCP glucuronide. The greater excretion of PCP glucuronide by seawater killifish may be responsible for the rapid elimination of PCP. PCP accumulation in killifish decreased with higher pH levels in both freshwater and seawater environments, but these differences were less than the effect of salinity. The results indicate that salinity can affect the accumulation and elimination of environmental pollutants in killifish.

Effects of isocyanuric acid on the monochlorodimedone chlorinating rates with free chlorine and ammonia chloramine in water.

Changes in monochlorodimedone (MCD) chlorinating rates with free chlorine (mixture of HOCl and OCl-) and ammonia monochloramine (NH2Cl) in water at pH 7 by the addition of isocyanuric acid (H3Cy) were determined at room temperature. Decreases in MCD absorbance at 290nm in equimolar (0.04mM) reactions of MCD and free available chlorine solutions containing H3Cy (0.01-1.60 mM) were recorded in a stopped-flow spectrophotometer. The rates indicate second-order reactions. Since the rate with free chlorine was high (> 7.6 x 10(6) M(-1) s(-1)), the amounts of free chlorine in the solutions could be distinguished from that of chlorinated cyanurates. The chlorinating rates with chlorinated cyanurates decreased with an increase in H3Cy concentrations. Plotting the rates against the molar ratio of chlorine to H3Cy showed a linear correlation and the rates with chlorinated cyanurates (H2ClCy) was estimated at 0.5 x 10(5) M(-1) s(-1). In contrast, the rates with the NH2Cl solution containing H3Cy increased with an increase in H3Cy concentrations, increasing from 1.2 x 10 to 2.7 x 10 M(-1) s(-1) by the addition of 1.55 mM H3Cy. The DPD color development rates (OD512/t1/2/M) with free available chlorine (0.015mM) declined from 1.3 x 10(5) to 0.9 x 10(5)M(-1) by the addition of 0.61 mM H3Cy.

The effects of salinity on pentachlorophenol accumulation and elimination by killifish (Oryzias latipes)

Fresh water and seawater acclimated (FWA and SWA) killifish (Oryzias latipes) were exposed to pentachlorophenol (PCP) at various salinities (1.2–18.7‰). The PCP accumulation in the fish decreased with increase of salinity. As the salinity increased [0‰ (freshwater) −18.6‰], the PCP clearance rate increased from 0.0097 to 0.0170 (h−1). A substantial increase of the clearance rate was observed when the salinity was over 9.3‰. The PCP uptake rate decreased from 20.8 to 10.6 (ml−1 g−1 fish h−1) with the increase of salinity. The uptake rate decreased at a lower salinity (⩽4.7‰). The excretion of PCP glucuronide (PCP-G) increased markedly at the salinity of 9.3‰, although that of PCP sulfate (PCP-S) did not change. The increase of PCP-G excretion may correspond to the increase of clearance rate. Abrupt transfer of FWA and SWA killifish to a PCP solution with a different salinity decreased the PCP accumulation and increased the PCP metabolite excretion with the increase of the salinity. However, the amount of PCP accumulated by FWA was greater than that by SWA killifish.

Hygienic Chemical Studies on Supplying Water Gas Chromatographic Method for Determination of PCB as Decachlorobiphenyl and Its Application for Measurement of PCB Removal by Purifying Process

Fundamental studies were carried out on the removal of polychlorinated biphenyls (PCB) contained in polluted source of supplying water. Activated carbon and coagulants such as aluminium sulfate and polyaluminium chloride (PAC) were used for removing PCB from water. In the present work, method for determination of PCB was also studied. Gaschromatographic determination of decachlorobiphenyl (DCB), which was obtained by complete chlorination of PCB with SbCl5, gave a good result. Among several preparations of PCB, Kanechlor-600 in water was determined as DCB in a good yield by gaschromatography, after extraction with n-hexane, concentration with Kuderna-Danish condenser, and chlorination with SbCl5 in a sealed glass tube at 200°for 1 hr. Removal of PCB from water was tested with Kanechlor-600 usnig the above method of determination. Two processes of treatment for aqueous solution containing 1ppm of Kanechlor-600 showed about 90% removal. One of them was the addition of activated carbon powder and coagulant at the same time, and the other was to pass the solution through a column of granular activated carbon. These processes were used in the purification system of water supplying work in some instances. It is considered that such higher purification system will be effective in removal of PCB from polluted water.

Hygienic Chemical Studies on Supplying Water. Decomposition of p-Hydroxycinnamic and Ferulic Acid with Hypochlorite in Water

The present series of work was undertaken to prove that there is no possibility for the presence of either ferulic acid or p-hydroxycinnamic acid in purified city water supplied by authorized water works. Both ferulic and p-hydroxycinnamic acids consume chlorine and are rapidly decomposed. They consume about 4 moles of hypochlorite for each mole of the substance, and the reaction is completed when the residual chlorine detected in the reaction mixture becomes about 0.1 ppm or less. This test for ferulic and p-hydroxycinnamic acids was carried out because some investigators attributed the incidence of a chronic bone disease, the so-called Kaschin-Beck disease, to city water, even if supplied by qualified water works, because of the presence of p-hydroxycinnamic (p-cumaric) and 4-hydroxy-3-methoxycinnamic (ferulic) acids, which were reported to have been detected in polluted river water used as a source of city water and which were found to produce changes in the cells of artilage tissue and salivary grands in young rats.