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Arsenic speciation in human urine reference materials using high-performance liquid chromatography with inductively coupled plasma mass spectrometric detection.

Six arsenic compounds including arsenocholine, arsenobetaine, dimethylarsinic acid, methylarsonic acid, arsenous acid and arsenic acid were separated by high-performance liquid chromatography (HPLC) on a Hamilton PRP-X100 anion-exchange column using isocratic elution and detected by inductively coupled plasma mass spectrometry (ICP-MS). This analytical procedure was applied to the speciation of arsenic compounds in human urine. The influence of urine matrix on the separation of arsenic compounds was evaluated and the determination of arsenic compounds was not hampered by the ArCl interference which has often been encountered in ICP-MS. Three human urine reference materials, SRM 2670 normal level, SRM 2670 elevated level and Lyphocheck urine metal control 1, were analyzed with respect to arsenic compounds by HPLC-ICP-MS. The results were found to be in good agreement with the certified total arsenic concentration in the reference materials. Six arsenic compounds were detected. Arsenobetaine was found to be present in all of the investigated human urine reference materials.

Arsenic↗

Evaluation of three antidotes on arsenic toxicity in the common earthworm (Lumbricus terrestris).

The common earthworm (Lumbricus terrestris) is being evaluated in our laboratories as a substitute for mice in metal toxicity studies. These two disparate species have enzymes in common, such as catalase, superoxide dismutase and glutathione-S-transferase. Also, worms respond similarly to these rodents for selenium and nickel toxicity. Worms are less sensitive, however, to metal toxicity. In this study earthworms were challenged with three different arsenic compounds: arsenite, arsenate and the vesicant phenyldichloroarsine (PDA). The median lethal dose for each arsenic compound was determined. The order of toxicity of the arsenic compounds to the worms was PDA > arsenite > arsenate (24 h LD50 values were 189.5, 191.0 and 519.4 mumol kg-1, respectively). Individual mammalian dithiol antidotes, namely the sodium salt of 2,3-dimercapto-1-propanesulfonic acid (DMPS), meso-dimercaptosuccinic acid (DMSA) or 2,3-dimercapto-1-propanol (BAL), were injected into the worms 5 min after various doses of the arsenic compound were administered. The decreases in acute toxicity values were recorded. All three antidotes protected the worms against arsenic toxicity with varying degrees of effectiveness. The protective action for the inorganic arsenic compounds was in the order DMPS > DMSA > BAL. For the organic arsenical, PDA, the most effective antidote was BAL.

Animals↗

Monomethylarsonic acid and dimethylarsinic acid: developmental toxicity studies with risk assessment.

BACKGROUND: The toxicity of arsenic compounds is highly dependent on the valence and methylation state of the compound. Although there is extensive published literature on the potential developmental toxicity of inorganic arsenic compounds, little exists on organic arsenic compounds and, in particular, studies conducted in accordance with conventional regulatory guidelines appropriate for risk assessment are rare. The organic arsenic compounds, monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV, also called cacodylic acid), are the active ingredients in pesticide products that are used mainly for weed control. MMAV and DMAV are also metabolites of inorganic arsenic formed intracellularly by most living organisms (animals, plants and bacteria). In mammals, this occurs predominantly in liver cells. METHODS: Conventional developmental toxicity studies of orally administered MMAV and DMAV in the Sprague-Dawley rat and New Zealand White rabbit were conducted in commercial contract laboratories in the late 1980 s for regulatory compliance. The results of these studies are summarized and presented to broaden the data available in the public domain. RESULTS: In both species, data shows an absence of dose-related effects at organic arsenic exposures that were not maternally toxic. MMAV doses of 0, 10, 100, and 500 mg/kg/day (rat) and 0, 1, 3, 7, and 12 mg/kg/day (rabbit) and DMAV doses of 0, 4, 12, and 36 mg/kg/day (rat) and 0, 3, 12, and 48 mg/kg/day (rabbit) were administered by oral gavage daily during organogenesis (Gestation Day [GD] 6-15, rat; GD 7-19, rabbit) and the litters examined at maternal sacrifice (GD 20, rat; GD 29, rabbit). After treatment with MMAV, maternal and fetal toxicity were observed at the highest doses of 500 mg/kg/day (rat) and 12 mg/kg/day (rabbit), but no treatment-related developmental toxicity at the lower doses, even in the presence of minimal maternal toxicity in the rat at 100 mg/kg/d. There was no evidence of teratogenicity associated with MMAV treatment. With DMAV, maternal and developmental toxicity were observed in the rat at 36 mg/kg/day, with a higher than spontaneous incidence of fetuses with diaphragmatic hernia. In the rabbit at 48 mg/kg/day, there was marked maternal toxicity, culminating for most females in abortion and with no surviving fetuses for evaluation. There was no treatment-related maternal or developmental toxicity in the rat or rabbit at 12 mg/kg/day. Based on pregnancy outcome, the developmental toxicity no observed adverse effect level (NOAEL) for orally administered MMAV were 100 and 7 mg/kg/day in the rat and rabbit, respectively, and for DMAV were 12 mg/kg/day in both species. CONCLUSIONS: Margins of exposure estimated based on conservative estimates of daily intakes of arsenic in all of its forms indicate that exposure to MMAV or DMAV at environmentally relevant exposure levels, by the oral route (the environmentally relevant route of exposure) is unlikely to pose a risk to pregnant women and their offspring.

Abnormalities, Drug-Induced↗

Metabolites of arsenic induced tetraploids and mitotic arrest in cultured cells.

The toxic effects of arsenic compounds on cell divisionwere studied, using Chinese hamster V79 cells. Seven arsenic compounds weretested. Inorganic arsenic compounds (arsenite and arsenate), which have beenfound in drinking water, inhibited cell growth at very low concentrations. Monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and trimethylarsineoxide (TMAO), which are methylated metabolites of inorganic arsenics, wereless cytotoxic than the inorganic arsenics themselves. The cytotoxicity ofthe three methylated metabolites decreased as the number of methyl groupsincreased. Arsenobetaine (AsBe) and arsenocholine (AsC), which have beenfound in some marine products, did not show any cytotoxicity. Threemethylated metabolites; MMA, DMA and TMAO induced mitotic arrest. Tetraploidyproduction was observed in cells exposed to DMA or TMAO. Arsenite, arsenate,AsBe and AsC did not induce mitotic arrest or tetraploids. These resultssuggest that MMA, DMA and TMAO exert some effect on cell division inmetaphase and may thereby give some clue as to the carcinogenic mechanism ofarsenic.

Animals↗

Diarsenic and tetraarsenic oxide inhibit cell cycle progression and bFGF- and VEGF-induced proliferation of human endothelial cells.

Arsenic trioxide (As2O3, diarsenic oxide) has recently been reported to induce apoptosis and inhibit the proliferation of various human cancer cells derived from solid tumors as well as hematopoietic malignancies. In this study, the in vitro effects of As2O3 and tetraasrsenic oxide (As4O6) on cell cycle regulation and basic fibroblast growth factor (bFGF)- or vascular endothelial growth factor (VEGF)-stimulated cell proliferation of human umbilical vein endothelial cells (HUVEC) were investigated. Significant dose-dependent inhibition of cell proliferation was observed when HUVEC were treated with either arsenical compound for 48 h, and flow cytometric analysis revealed that these two arsenical compounds induced cell cycle arrest at the G1 and G2/M phases--the increases in cell population at the G1 and G2/M phase were dominantly observed in As2O3- and As4O6-treated cells, respectively. In both arsenical compounds-treated cells, the protein levels of cyclin A and CDC25C were significantly reduced in a dose-dependent manner, concomitant to the reduced activities of CDK2- and CDC2-associated kinase. In G1-synchronized HUVEC, the arsenical compounds prevented the cell cycle progression from G1 to S phase, which was stimulated by bFGF or VEGF, through the inhibition of growth factor-dependent signaling. These results suggest that arsenical compounds inhibit the proliferation of HUVEC via G1 and G2/M phase arrest of the cell cycle. In addition, these inhibitory effects on bFGF- or VEGF-stimulated cell proliferation suggest antiangiogenic potential of these arsenical compounds.

Antineoplastic Agents↗

Arsenobetaine in the red crab, Chionoecetes opilio.

The meat of the red crab, Chionoecetes opilio, caught near the central coast the Japan Sea, was extracted with methanol. The arsenic compounds were isolated from this extract and purified by anion and cation exchange chromatography and thin-layer chromatography. Three arsenic compounds were detected. The major arsenic compound, identified as arsenobetaine by TLC, proton NMR spectroscopy, and high pressure liquid chromatography with an atomic absorption spectrometer as an arsenic-specific detector, accounted for 90% of the total arsenic in the crab meat. The other two arsenic compounds could not be identified because of insufficient amounts available for analysis.

Animals↗

Chemical speciation of arsenic in the livers of higher trophic marine animals.

Concentrations of total arsenic and individual arsenic compounds were determined in livers of cetaceans (Dall's porpoise and short-finned pilot whale), pinnipeds (harp and ringed seals), sirenian (dugong), and sea turtles (green and loggerhead turtles) to characterize arsenic accumulation profiles in higher trophic marine animals. Hepatic arsenic concentrations in sea turtles were highest among the species examined. Chemical speciation of arsenic revealed that arsenobetaine was the major arsenic compound in almost all the species. In contrast, arsenobetaine was a minor constituent in dugong. Dimethylarsinic acid, methylarsonic acid, arsenocholine, tetramethylarsonium ion, arsenite, and an unidentified arsenic compound were also detected as minor constituents. However, the composition of arsenic compounds was different among these species. These results might reflect the differences in the metabolism of arsenic and/or the compositions of arsenic compounds in their preys. To our knowledge, this is the first report on the large variation in the composition of arsenic species in liver of marine mammals and sea turtles.

Animals↗

Reduction of inorganic compounds with molecular hydrogen by Micrococcus lactilyticus. I. Stoichiometry with compounds of arsenic, selenium, tellurium, transition and other elements.

Woolfolk, C. A. (University of Washington, Seattle) and H. R. Whiteley. Reduction of inorganic compounds with molecular hydrogen by Micrococcus lactilyticus. I. Stoichiometry with compounds of arsenic, selenium, tellurium, transition and other elements. J. Bacteriol. 84:647-658. 1962.-Extracts of Micrococcus lactilyticus (Veillonella alcalescens) oxidize molecular hydrogen at the expense of certain compounds of arsenic, bismuth, selenium, tellurium, lead, thallium, vanadium, manganese, iron, copper, molybdenum, tungsten, osmium, ruthenium, gold, silver, and uranium, as well as molecular oxygen. Chemical and manometric data indicate that the following reductions are essentially quantitative: arsenate to arsenite, pentavalent and trivalent bismuth to the free element, selenite via elemental selenium to selenide, tellurate and tellurite to tellurium, lead dioxide and manganese dioxide to the divalent state, ferric to ferrous iron, osmium tetroxide to osmate ion, osmium dioxide and trivalent osmium to the metal, uranyl uranium to the tetravalent state, vanadate to the level of vanadyl, and polymolybdate ions to molybdenum blues with an average valence for molybdenum of +5. The results of a study of certain other hydrogenase-containing bacteria with respect to their ability to carry out some of the same reactions are also presented.

Arsenic↗

Chemical form-dependent induction of hepatic zinc-thionein by arsenic administration and effect of co-administered selenium in mice.

Four arsenic compounds (m-arsenite, arsenate, methylarsonate (MMA), and dimethylarsinate (DMA) were administered to mice, either orally or by intraperitoneal injection, and the amounts of induced hepatic zinc-thionein (Zn-Th) were determined to investigate the chemical form dependency in metallothionein induction by arsenic. Several mice died within 24 h following intraperitoneal injection. The toxicity estimated from the lethality was in the order of m-arsenite greater than arsenate much greater than DMA approximately equal to MMA. Although all 4 arsenic compounds more or less induced Zn-Th following intraperitoneal injection, the dose of inorganic arsenic compounds observed to cause induction was one order lower than that of organic arsenic compounds. The induction of hepatic Zn-Th was also observed following oral administration, and inorganic arsenic compounds were again found to be more effective inducers via this route. To study the interactions of m-arsenite and selenite with regard to the amounts of Zn-Th induced, the two compounds were co-administered intraperitoneally. The amount of hepatic Zn-Th induced by the co-administration was one-fifth of that observed after selenite administration, and was almost the same as that after m-arsenite injection. Namely, when co-administered m-arsenite had the effect of lowering the level of Zn-Th induced following selenite administration, but the converse phenomenon was not observed.

Animals↗

Studies of cytogenetic effects of sodium arsenicals on mammalian cells in vitro.

The cytotoxic and cytogenetic effect of sodium arsenite and sodium arsenate on Chinese hamster ovary (CHO) cells is reported. Chromosome aberrations were induced with both arsenic compounds. Trivalent arsenic was more clastogenic than pentavalent arsenic. Sodium arsenite was also shown to produce increased sister chromatid exchange in CHO cells and increased chromosome breakage in human lymphocytes.

Animals↗

Arsenic burden of cooked rice: Traditional and modern methods.

Arsenic contamination of rice by irrigation with contaminated groundwater and secondarily increased soil arsenic compounds the arsenic burden of populations dependent on subsistence rice-diets. The arsenic concentration of cooked rice is known to increase with the arsenic concentration of the cooking water but the effects of cooking methods have not been defined. We tested the three major rice cooking procedures followed globally. Using low-arsenic water (As < 3 microg/L), the traditional method of the Indian subcontinent (wash until clear; cook with rice: water::1:6; discard excess water) removed up to 57% of the arsenic from rice containing arsenic 203-540 microg/kg. Approximately half of the arsenic was lost in the wash water, half in the discard water. A simple inexpensive rice cooker based on this method has been designed and used for this purpose. Despite the use of low-arsenic water, the contemporary method of cooking unwashed rice at rice:water::1:1.5-2.0 until no discard water remains did not modify the arsenic content. Preliminary washing until clear did remove 28% of the rice arsenic. The results were not influenced by water source (tubewell, dug well, pond or rain); cooking vessel (aluminium, steel, glass or earthenware); or the absolute weight of rice or volume of water. The use of low-As water in the traditional preparation of arsenic contaminated rice can reduce the ingested burden of arsenic.

Arsenic↗

Treatment of acute promyelocytic leukemia with ATRA and As2O3: a model of molecular target-based cancer therapy.

Most acute promyelocytic leukemia (APL) cases have t(15;17)(q22;q21) chromosomal translocation and PML-RARalpha chimeric gene which blocks granulocytic differentiation. The introduction of all-trans-retinoic acid (ATRA) and arsenic compounds, especially arsenic trioxide (As(2)O(3)), has provided good models to study not only differentiation and/or apoptosis therapy but also molecular target-based cancer treatment. In vivo and in vitro investigations have shown that both agents are able to induce differentiation of APL cells: ATRA tends to induce terminal differentiation, while low-dose As(2)O(3) can induce partial differentiation. Significant progress has been made in understanding the molecular mechanisms of APL pathogenesis and differentiation therapy. Pharmacological concentrations (0.1 approximately 1 microM) of ATRA derepresses transcription by releasing CoR from, and recruiting CoA to PML-RARalpha, whereas As(2)O(3) triggers a rapid degradation of PML-RARalpha. In fact, the two drugs act on the same oncoprotein through targeting different moieties and in distinct ways and thereby abrogate its dominant-negative effects on regulatory pathways necessary for granulocytic differentiation. As to apoptosis, it is clear that high-dose As(2)O(3) can induce mitochondria-mediated cell death pathway in a thiol-dependent manner, while the mechanism of ATRA-induced apoptosis needs further elucidation. Transcriptomic and proteomic analysis are also expected to find new molecular targets. It is the hope that what we have learnt from APL will benefit further developments of anti-leukemia therapy.

Animals↗

[Etiology of bronchial cancer: smoking, passive smoking, environment and occupation].

The inhaled tobacco smoke is the most important determinant in the etiology of lung cancer and there is a clear dose-effect relation between lung cancer risk and the duration of smoking, the number of cigarettes and the intensity of inhalation. The opinions about lung cancer risk from passive smoking are divided and the published data are still in discussion. Occupational substances include chromates, nickel, beryllium, alkylated compounds, vinylchloride, arsenic compounds and in particular asbestos. Fortunately air pollution has no or small part in the etiology of lung cancer.

Carcinogens, Environmental↗

The carcinogenicity of arsenic.

A carcinogenic role of inorganic arsenic has been suspected for nearly a century. Exposure to inorganic arsenic compounds occurs in some occupational groups, e.g., among smelter workers and workers engaged in the production and use of arsenic containing pesticides. Substantial exposure can also result from drinking water in certain areas and the use of some drugs. Tobacco and wine have had high As concentrations due to the use of arsenic containing pesticides. Inorganic arsenic compounds interfere with DNA repair mechanisms and an increased frequency of chromosomal aberrations have been observed among exposed workers and patients. Epidemiological data show that inorganic arsenic exposure can cause cancer of the lung and skin. The evidence of an etiologic role of arsenic for angiosarcoma of the liver is highly suggestive; however, the association between arsenic and cancer of other sites needs further investigation. No epidemiological data are available on exposure to organic arsenic compounds and cancer. Animal carcinogenicity studies involving exposure to various inorganic and organic arsenic compounds by different routes have been negative, with the possible exception of some preliminary data regarding lung cancer and leukemia. Some studies have indicated an increased mortality from lung cancer in populations living near point emission sources of arsenic into the air. The role of arsenic cannot be evaluated due to lack of exposure data. Epidemiological data suggest that the present WHO standard for drinking water (50 micrograms As/l.) provides only a small safety margin with regard to skin cancer.

Air Pollutants↗

The nephrotoxic effect of the ototoxic compound atoxyl.

The arsenical compound atoxyl has been used in labyrinthine research because of its documented effects both on cells engaged in an active transport of ions (secretory epithelia) and sensory epithelia (cochlear hair cells and vestibular sensory cells type I and type II.) In the present experiments both the kidney and the structures of the inner ear were studied. The renal tubules were damaged by exposure to atoxyl. Tubular casts, haemorrhages (both in the tubules and in the renal calices) and tubular epithelial cell necrosis occurred. A common denominator in the ototoxic and the nephrotoxic actions of acute atoxyl poisoning might be a disturbance of the very active ion transport systems of the cells involved.

Animals↗

Placental transfer of arsenic to fetus of Dall's porpoises (Phocoenoides dalli).

Concentrations of total arsenic and individual arsenic compounds were determined in liver, muscle, kidney and blubber of mother and fetus of Dall's porpoises collected from off Sanriku, Japan, in the year 2000 to characterize the placental transfer of arsenic to fetus in cetaceans. Arsenic was detected in all the tissues of Dall's porpoises. Total arsenic concentrations in liver, kidney, muscle and blubber were 0.76, 0.69, 0.35 and 0.55 microg/g wet wt, respectively, for mother and 0.28, 0.23, 0.26 and 0.07 microg/g wet wt, respectively, for fetus. In all the tissues, concentrations of total arsenic in mother Dall's porpoise were higher than in fetus. Arsenic speciation revealed that arsenobetaine was the major arsenic compound in liver, kidney and muscle of both mother and fetus. The percentage of arsenobetaine to total arsenic ranged from 76.0 to 91.0% in the tissues. Dimethylarsinic acid, arsenocholine, methylarsonic acid and an unidentified arsenic compound were also detected in tissues of both mother and fetus as minor constituents, whereas tetramethylarsonium ion was not detected in tissues of the fetus. These results suggest that arsenobetaine, dimethylarsinic acid, arsenocholine and methylarsonic acid are transferable from mother to fetus in Dall's porpoises. To our knowledge, this is the first report on placental transfer of arsenic compounds to fetus in marine mammals.

Adipose Tissue↗

Determination of 'arsenosugars' in algae with anion-exchange chromatography and an inductively coupled plasma mass spectrometer as element-specific detector.

The retention behavior of four naturally occurring dimethylarsinoylribosides with -CH2-CHOH-CH2X (X = OH, HO3POCH2CHOHCH2OH, SO3H, OSO3H) as aglycones, of arsenous acid, arsenic acid, methylarsonic acid, and dimethylarsinic acid was investigated on a Hamilton PRP-X100 anion-exchange column with aqueous solutions of ammonium dihydrogen phosphate (20 mmol/L) in the pH range of 3.8-9.0 as mobile phase. A HP 4500 inductively coupled plasma mass spectrometer (ICP-MS) served as arsenic-specific detector. The influence of pH, temperature, and the concentration of methanol in the mobile phase on the retention times of these arsenic compounds was explored. An aqueous 20 mM ammonium dihydrogen phosphate solution at pH 5.6 at a column temperature of 40 degrees C was considered optimal as it allowed the separation of seven of the arsenic compounds within 16 min. Only arsenous acid and the ribose with the glycerol aglycone have overlapping signals with both migrating almost with the solvent front. At a concentration of 0.50 ng As mL(-1) the relative standard deviations (n = 3) of the signal areas of the eight arsenic compounds was in the range from 3.5 to 8.1%. The linear calibration curves (peak areas) from 0.5 to 10 ng/mL had correlation coefficients > 0.997. Extracts obtained from the brown algae Fucus spiralis and Halidrys siliquosa were chromatographed under the optimized conditions. Both species contained the sulfate riboside as the major arsenic compound (approximately 55% of total extractable arsenic) together with the sulfonate- and phosphate riboside. Arsenic acid was a significant constituent of Halidrys siliquosa (approximately 6.5%), but was not detected in Fucus spiralis.

Arsenicals↗