The toxicokinetics and distribution of 2-hydroxyethyl methacrylate in mice.

The cytotoxicity of dental composites has been attributed to the release of residual monomers from polymerized resin-based composites due to the degradation processes or the incomplete polymerisation of materials. 2-Hydroxyethyl methacrylate (HEMA) is one of the major components released from dental resin-based composites. It was shown in vitro that HEMA was released into the adjacent biophase from such materials during the first days after placement. In this study uptake, distribution, and excretion of 14C-HEMA applied via gastric tube or subcutaneous administration at dose levels well above those encountered in dental care were examined in mice to test the hypothesis that HEMA can reach cytotoxic levels in mammalian tissues. 14C-HEMA was taken up rapidly from the stomach and intestines after gastric administration and was widely distributed in the body following administration by each route. Most 14C was excreted within one day as (14)CO(2). Two metabolic pathways of 14C-HEMA can be described. The peak HEMA levels in all tissues examined after 24h were lower than known toxic levels. Therefore the study did not support the hypothesis.

Inhibition of poly(ADP-ribose) polymerase (PARP) influences the mode of sulfur mustard (SM)-induced cell death in HaCaT cells.

Sulfur mustard (SM) is a bifunctional alkylating agent. Its primary toxic consequence is severe skin damage with blisters, occurring after skin contact. These vesicant properties of SM have been linked to cell death of proliferating keratinocytes in the basal layer of the skin. Catalytic activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP-1) has been demonstrated to be a major event in response to high levels of DNA damage, and PARP-1 activation may be part of apoptotic signaling. In other contexts, overstimulation of PARP-1 triggers necrotic cell death because of rapid consumption of its substrate, beta-nicotinamide adenine dinucleotide (NAD+) and the consequent depletion of ATP. These findings prompted us to evaluate whether SM induces apoptosis in keratinocytes like HaCaT cells and to determine whether blocking of PARP enzyme activity with 3-aminobenzamide (3AB) can influence the mode of cell death. HaCaT cells were exposed to SM (10-1,000 microM; 30 min) and then cultivated in SM-free medium with or without 3AB for up to 48 h. This treatment resulted in a time and SM dose-dependent increase of apoptotic cell death characterized by PARP-1 cleavage and DNA fragmentation during the experimental period. After just 45 min of exposure to 1 mM SM, we observed a significant increase in PARP-1 activity in HaCaT cells. About 6 h after exposure, intracellular ATP levels were diminished by 22%, which seemed to be completely prevented by the addition of 3AB directly after exposure. However, 18 h later, this 3AB effect on the SM concentration-dependent loss of ATP was no longer detectable. Interestingly, the effect of SM on total cell viability was not changed by 3AB. However, the mode of cell death was influenced by 3AB exhibiting an increase of apoptotic cells and a concomitant decrease of necrotic HaCaT cells during the first 24 h after SM exposure. Our results indicate that SM concentrations of 1 mM or higher induce a prominent PARP activation leading to ATP depletion and necrosis. In contrast, lower concentrations of SM cause minor PARP activation and, especially, PARP-1 cleavage by caspase 3 without ATP depletion. Because ATP is required for apoptosis, we suggest that ATP acts as an early molecular switch from apoptotic to necrotic modes of SM-induced cell death, at least at high concentrations (> or =1 mM). Thus, the observed early proapoptotic effect of 3AB at lower SM concentrations may point to the influence of ATP-independent cell-death regulating mechanisms.

Apoptosis in sulfur mustard treated A549 cell cultures.

The chemical warfare agent sulfur mustard (SM) is a strong alkylating agent that leads to erythema and ulceration of the human skin several hours after exposure. Although SM has been intensively investigated, the cellular mechanisms leading to cell damage remain unclear. Apoptosis, necrosis and direct cell damage are discussed. In this study we investigated apoptotic cell death in pulmonary A549 cells exposed to SM (30-1000 microM, 30 min). 24 h after SM exposure DNA breaks were stained with the TUNEL method. Additionally, A549 cells were lysed and cellular protein was transferred to SDS page and blotted. Whole PARP as well as PARP cleavage into the p89 fragment, an indicator of apoptosis, were detected by specific antibodies. SM concentration dependent increase in TUNEL positive cells and PARP cleavage showed that SM is an inducer of apoptosis. It has been previously suggested that AChE is activated during apoptotic processes and may be involved in apoptosis regulation. Therefore, we examined AChE activity in A549 cells upon induction of apoptosis by SM (100-500 microM). Increased AChE activity was found in SM treated A549 cell cultures examined as determined by the Ellman's assay and by western blot. AChE activity showed a strong correlation with TUNEL positive cells. However, the broad caspase inhibitor zVAD and the PARP-inhibitor 3-aminobenzamide had no protective effect on A459 cells measured with AChE activity and frequency of TUNEL positive cells. In summary, our studies demonstrate that AChE activity may be a potential marker of apoptosis in A549 cells after SM injury. To what extent AChE is involved in apoptosis regulation during SM poisoning has to be further investigated.

Effects of Lewisite on cell membrane integrity and energy metabolism in human keratinocytes and SCL II cells.

Lewisite is a highly toxic arsenic compound which can cause skin damage. In the present study effects of Lewisite on cell membrane integrity and energy metabolism as well as antidotal effects of DL-2,3-dimercaptopropanesulfonate (DMPS), and meso-2,3-dimercaptosuccinic acid (m-DMSA) were investigated in a keratinocyte derived cell line (SCL II) and primary human keratinocytes (HK). Cells were incubated in Lewisite (60 microM) containing medium for 5 min. During the following 6 h lactate dehydrogenase (LDH) activity in the supernatant, intracellular ATP content, tetrazolium reduction, glucose consumption and lactate formation were measured. Glucose consumption and lactate production were decreased in both cell lines after Lewisite exposure. In SCL II cells an increase of LDH activity in the supernatant, a decrease of ATP content, and an impaired ability to reduce tetrazolium was found 3 h after Lewisite exposure. In HK cultures tetrazolium reduction was significantly decreased already after 2 h, whereas LDH increase in the supernatant and ATP content decrease occurred only at 6 h after Lewisite exposure. When DMPS or m-DMSA was added directly after Lewisite exposure to SCL II cells, glucose consumption and lactate formation were restored and LDH leakage was prevented. SCL II cells might be more prone to membrane damage whereas in keratinocytes mitochondrial impairment seems to be the predominant effect of Lewisite.

Distribution and excretion of TEGDMA in guinea pigs and mice.

The monomer triethyleneglycoldimethacrylate (TEGDMA) is used as a diluent in many resin-based dental materials. It was previously shown in vitro that TEGDMA was released into the adjacent biophase from such materials during the first days after placement. In this study, the uptake, distribution, and excretion of 14C-TEGDMA applied via gastric, intradermal, and intravenous administration at dose levels well above those encountered in dental care were examined in vivo in guinea pigs and mice as a test of the hypothesis that TEGDMA reaches cytotoxic levels in mammalian tissues. 14C-TEGDMA was taken up rapidly from the stomach and small intestine after gastric administration in both species and was widely distributed in the body following administration by each route. Most 14C was excreted within one day as 14CO2. The peak equivalent TEGDMA levels in all mouse and guinea pig tissues examined were at least 1000-fold less than known toxic levels. The study therefore did not support the hypothesis.

DMPS-arsenic challenge test. I: Increased urinary excretion of monomethylarsonic acid in humans given dimercaptopropane sulfonate.

The purpose of the present study was to evaluate in a novel manner the arsenic exposure of humans living in two towns in Northeastern Chile. Residents of one town drink water containing 593 microg As/l. Those in the control town drink water containing 21 microg As/l. Our hypothesis was that the administration of the chelating agent, 2,3-dimercaptopropane-1-sulfonic acid, Na salt (DMPS, DIMAVAL) would increase the urinary excretion of arsenic, alter the urinary profile of arsenic species and thus result in a better indication of the body load of arsenic and a better biomarker for arsenic exposure. The method used to evaluate these subjects was to give them 300 mg DMPS by mouth, after an overnight fast, and collect urine at specified time periods. The urine samples were analyzed for inorganic arsenic, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and total arsenic by hydride generation and atomic absorption spectrophotometry. The results indicated that: 1) During the 2-hr period after DMPS administration, MMA represented 42%, inorganic As, 20 to 22% and DMA, 37 to 38% of the total urinary arsenic. The usual range of the MMA percentage in human urine has been 10 to 20%. The % MMA increased almost equally for both the arsenic-exposed and control subjects. 2) The exposed subjects had a greater urinary excretion of total arsenic, before and after DMPS administration, than the control subjects. 3) Although buccal cells were obtained only from a few subjects, the prevalence of mononucleated buccal cells, an indication of genotoxicity, was 5-fold greater for those who consumed drinking water with the higher arsenic content than among control subjects. Our conclusions are that 1) DMPS has a highly specific effect in humans on MMA metabolism and/or urinary excretion; 2) the human body stores substantial amounts of arsenic; and 3) the urinary arsenic concentration after DMPS administration may be more indicative of the body burden of arsenic because it was greater than that found before DMPS was given.

Antidotal efficacy of newly synthesized dimercaptosuccinic acid (DMSA) monoesters in experimental arsenic poisoning in mice.

The efficacy of four newly synthesized monoesters of meso-2,3-dimercaptosuccinic acid (DMSA), mono-i-amyl- (Mi-ADMS), mono-n-amyl- (Mn-ADMS), mono-i-butyl- (Mi-BDMS), and mono-n-butyl-meso-2,3-dimercaptosuccinate (Mn-BDMS) in increasing survival and arsenic elimination in experimental arsenic poisoning was investigated. Male mice (strain NMRI) received arsenite sc (survival study: 130 mumol/kg, 7 mice/group; elimination study: 85 mumol/kg (LD5) together with a tracer dose of 73As(III), 6 mice/group). After 30 min mice were treated with 0.7 mmol/kg of DMSA or a monoester ip or via gastric tube (ig). Control animals received saline ip. In the survival study mice were observed for 30 days. In the elimination study, the 73-arsenic content of several organs (blood, liver, heart, lung, kidneys, spleen, testes, brain, small intestine, large intestine, muscle, and skin) was measured 0.5, 2, 4, 6, and 8 hr after the arsenic injection using a gamma counter. Survival increased correspondingly well with the increase of arsenic elimination. DMSA, Mi-ADMS, Mn-ADMS, Mi-BDMS, and Mn-BDMS markedly decreased arsenic content in most organs as soon as 1.5 hr after treatment. Only in small and large intestine were higher arsenic amounts found, indicating a shift in arsenic elimination from the renal to the fecal route, and thereby suggesting a protective effect for the kidneys. Given ip, the monoesters turned out to be similarly as effective as the parent drug DMSA. Following ig treatment, the DMSA monoesters Mi-ADMS and Mn-ADMS seemed to be superior to DMSA with regard to survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Zinc-induced arsenite tolerance in mice.

The mechanism of tolerance to arsenic toxicity is not known. Recently it has been shown that arsenic induces metallothionein (MT), which is a sulfhydryl-rich, metal-binding protein that decreases the toxicity of a number of metals. The present studies were designed to examine the role of MT in arsenic toxicity. Zinc (Zn) pretreatment (1000 mumol/kg, sc) markedly increased hepatic MT (150-fold over controls), and also protected against the lethal effects of arsenite (130 mumol/kg, sc). However, no correlation was found between the ability of various known MT inducers (Zn, Cd, arsenite, monomethylarsenite, alpha-hederin, or oleanolic acid) to increase hepatic MT and to protect against arsenic lethality in mice. To examine the mechanism of Zn protection against arsenic toxicity, the subcellular distribution of arsenite in liver, kidney, and small intestine was determined 2 hr after arsenite injection. Zn pretreatment did not markedly alter the amount of arsenic-73 in the cytosol or the various cellular organelles (nuclei, mitochondria, microsomes) in liver kidney, or small intestine. There was also very little arsenic-73 bound to MT in the cytosol of the Zn-pretreated mice, as determined by G-75 gel-filtration chromatography. In mice pretreated with Zn (1000 mumol/kg, sc) and subsequently injected with arsenite-73 (115 mumol/kg, sc), the arsenic-73 content in blood, heart, lung, kidneys, spleen, muscle, and skin was lower than in controls, indicating increased arsenic elimination in Zn-pretreated mice. In conclusion, Zn pretreatment protects mice against arsenite toxicity, but the mechanism of tolerance does not appear to be induction of MT.

Effect of various antidotes on the biliary and intestinal excretion of arsenic in situ and into the feces in vivo in guinea-pigs after injection of As2O3.

The effect of various antidotes on the excretion of arsenic into the feces in vivo and on the biliary and enteric excretion in situ was investigated on segments of jejunum and colon in anesthetized guinea-pigs using the pendular perfusion technique, according to Henning and Forth (1982). In the in situ experiments guinea-pigs received As2O3 (0.02 mmol As(III)/kg) and 30 min later, British-Anti-Lewisite (BAL), dimercaptopropanesulfonic acid (DMPS), dimercaptosuccinic acid (DMSA) or 2,3-bis-(acetylthio)propanesulfonamide (BAPSA) (0.1 or 0.7 mmol/kg each) into the jugular vein. In the in vivo experiments guinea-pigs received As2O3 s.c. (same dose as above) and 30 min later the same antidotes (0.1 mmol/kg i.p.). The feces were collected for 24 h and the arsenic content measured. During the 60-min perfusion period the amount of arsenic excreted into the jejunum or colon was only 3% or 0.4% of the dose administered, respectively. Of the arsenic dose, 8% was found in the bile. None of the antidotes had an effect on the arsenic excretion into the jejunum or colon. No change in biliary excretion was found in animals treated with BAL, 0.1 or 0.7 mmol/kg, respectively. DMSA, BAPSA or DMPS, 0.1 mmol/kg, increased the biliary excretion of arsenic to 14, 33, or 43% of the dose administered and after 0.7 mmol/kg to 29, 37, or 42%, respectively. Furthermore, a significant increase (P > 0.05) was found for the bile/blood concentration ratio in the following order: control < BAL < DMSA < BAPSA approximately DMPS.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of metallothionein by alpha-hederin.

alpha-Hederin (alpha-Hed) is a triterpenoid saponin that has been shown to protect against some hepatotoxicants. This study examined the protective effect of alpha-Hed against cadmium (Cd) hepatotoxicity and the mechanism of protection. alpha-Hed pretreatment (100 mumol/kg, sc) dramatically decreased Cd (3.7 mg/kg, iv) hepatotoxicity as indicated by a reduction of serum alanine aminotransferase and sorbitol dehydrogenase, as well as by histopathological examination. alpha-Hed did not produce protection by decreasing the distribution of Cd to the liver, as higher amounts of Cd were found in the liver of alpha-Hed-pretreated mice. However, there was a marked alteration in subcellular distribution of Cd in the alpha-Hed-pretreated mice, with much less Cd distributing to nuclei, mitochondria, and microsomes and more in the cytosol. The increased cytosolic Cd was found primarily bound to a low-molecular-weight protein, metallothionein (MT). alpha-Hed (10-300 mumol/kg, sc) produced a dose-dependent increase in hepatic MT with a 100-fold increase over controls 24 hr after a single injection of 100 mumol/kg, as determined by the Cd/hemoglobin assay. The hepatic MT increase produced by alpha-Hed is relatively long lasting, in that it is still eight times control values 6 days after a single administration. The induction of MT was also relatively specific for the liver, as little or no increase in MT was observed in other tissues. Furthermore, alpha-Hed increased both hepatic MT-I and MT-II levels. Northern blot analysis revealed that alpha-Hed rapidly increased MT mRNA levels. In conclusion, alpha-Hed decreases the hepatotoxicity of Cd by inducing MT, which binds Cd in the cytosol, and thus reduces the amount of Cd in the critical cellular organelles. alpha-Hed is an effective inducer of both MT-I and MT-II in liver, and this effect is associated with an increase in MT mRNA.

Oleanolic acid protects against cadmium hepatotoxicity by inducing metallothionein.

Oleanolic acid (OA) is a triterpenoid compound that has been shown to protect against some hepatotoxicants and is used in China to treat hepatitis. This study was conducted to examine the protective effects of OA against cadmium (Cd)-induced liver injury in mice and the mechanism of protection. OA (100 mg/kg x 3 days) pretreatment dramatically decreased Cd (3.7 mg/kg i.v.)-induced liver injury as indicated by decreased serum activities of alanine aminotransferase and sorbitol dehydrogenase, as well as by histopathological observation. To examine the mechanism of protection, the distribution of Cd to major organs and the hepatic subcellular distribution of Cd were determined 2 hr after 109Cd injection (3.5 mg/kg of Cd and 10 microCi/mg of Cd i.v.). OA did not reduce the amount of Cd in liver, but significantly altered the hepatic subcellular distribution of Cd, with more Cd in hepatic cytosol bound to metallothionein (MT), and with less Cd in other organelles and proteins. OA produced an approximately 30-fold increase in hepatic MT, but had no appreciable effects on MT levels of five other organs. Furthermore, OA increased both hepatic MT-I and MT-II levels, as determined by high-performance liquid chromatography/atomic absorption spectrophotometry. Northern blot analysis revealed that OA increases MT mRNA expression. In summary, OA pretreatment protects against Cd-induced hepatotoxicity by inducing MT. MT bound Cd in the cytosol, and thus decreased the amount of Cd in other critical organelles and proteins. OA is a hepatic MT inducer for both MT-I and MT-II isoforms, and this effect is due, at least in part, to an increased MT mRNA accumulation.

Induction of metallothionein by arsenicals in mice.

Metallothionein (MT) is a sulfhydryl-rich, metal-binding protein that provides protection against metal toxicity. MT is induced by acute stress, hormones, metals, and various organic compounds. Recently, arsenicals have also been shown to induce MT. However, the mechanism and character of MT induction by arsenicals is unknown. Therefore, the effect of various arsenic forms on the tissue concentration of MT was determined. Mice were injected sc with various doses of arsenite [As(III)], arsenate [As(V)], monomethylarsenate (MMAA), and dimethylarsenate (DMAA), and MT content in the liver was measured 24 hr later by the Cd-hemoglobin radioassay. As(III) is a potent hepatic MT inducer in that a 30-fold increase in MT was observed at the dose of 85 mumol/kg. In comparison, it took 3-, 50-, and 120-fold higher molar amounts of As(V), MMAA, and DMAA, respectively to produce a similar effect. MMAA produces the largest increase in hepatic MT (80-fold), followed by As(III) (30-fold), As(V) (25-fold), and DMAA (10-fold). However, none of the arsenicals induced MT in mouse primary hepatocyte cultures. Both MT-I and MT-II were coordinately induced by As(III), As(V), and MMAA. MT induction by As(III) was further characterized following sc administration of arsenite (85 mumol/kg). Hepatic MT induction peaked at 24 hr, and in addition to the liver, As(III) also increased MT in kidney, spleen, stomach, intestine, heart, and lung. MT-I mRNA increased 24-, 52-, and 11-fold at 3, 6, and 15 hr after As(III) administration. This induction profile is similar to that observed after Zn or Cd exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic efficacy of new dimercaptosuccinic acid (DMSA) analogues in acute arsenic trioxide poisoning in mice.

The therapeutic efficacy of six newly synthesized analogues of dimercaptosuccinic acid (DMSA) was investigated in acute arsenic trioxide poisoning in mice. Meso-2,3-di(acetylthio)succinic acid (DATSA) and meso-2,3- di(benzoylthio)succinic acid (DBTSA) are analogues of DMSA with protected thiol groups ("prodrugs"), and DMDMS, DEDMS, DnPDMS, and DiPDMS are various di-esters of DMSA with methyl, ethyl, n-propyl, and isopropyl alcohols, respectively. Thirty minutes after s.c. injection of an LD80 of arsenic trioxide (65 mumol/kg) male NMRI mice were treated with a single equimolar dose (0.7 mmol/kg) of DMSA i.p. or one of the analogues i.p. or via gastric tube (i.g.). Control animals received arsenic trioxide and saline 30 min later. The survival rate was recorded for 30 days. All of the animals treated with DMSA i.p. survived and all controls died within 2 days. Administered i.g., DATSA and DBTSA increased the survival rate to 29% and 43%, and injected i.p. to 86%. Treatment with DMDMS i.p. and i.g., and with DEDMS, DnPDMS, and DiPDMS i.g. did not reduce lethality. Given i.p., DnPDMS increased the survival rate to 72%, and DEDMS and DiPDMS to 86%, respectively. To investigate the efficacy of the DMSA analogues in reducing the tissue content of arsenic, male NMRI mice received an s.c. injection of an LD5 of arsenic trioxide containing a tracer dose of 73-As(III) (42.5 mumol/kg body wt). Thirty minutes later, saline (controls) or a single equimolar dose (0.7 mmol/kg) of DMSA i.p., or one of the analogues i.p. or i.g. was administered. The arsenic content of various organs (blood, liver, kidneys, heart, lungs, spleen, small intestine, large intestine, brain, testes, skeletal muscle, and skin) at 30 min, 2 h, 4 h, 6 h, and 8 h after the arsenic injection was measured using a gamma counter.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of various antidotes on biliary excretion of arsenic in isolated perfused livers of guinea pigs after acute experimental poisoning with As2O3.

The effect of the dithiols British Anti-Kewisite (BAL), dimercaptopropanesulfonic acid (DMPS), dimercaptosuccinic acid (DMSA) and a new metal binding agent 2,3-bis-(acetylthio)- propanesulfonamide (BAPSA) on the biliary excretion of arsenic in perfused livers of guinea pigs after acute experimental poisoning with As2O3 was investigated. Guinea pigs received As2O3, 10.0 mg/kg subcutaneously at 9 a.m. as a single injection. One hour after the injection the livers were perfused (2.5 ml x min.-1 x g-1 liver) with Krebs-Henseleit buffer and glucose for 80 min. After 40 min. of saline perfusion (control) 0.1 or 0.7 mmol/l BAL, DMSA, DMPS, or BAPSA were added to the perfusate and arsenic elimination in the bile and effluent perfusate was measured. The biliary excretion of arsenic in control livers between 40 and 80 min. was 0.7% of the total arsenic liver content before perfusion (= arsenic liver content after perfusion + portion excreted in the bile+perfusate). After antidote addition (0.1 mmol/l) the excretion was 0.2% for livers perfused with BAL, 6.8% for DMSA, 10.6% for DMPS, and 11.1% for BAPSA, respectively. After 0.7 mmol/l antidote the excretion of arsenic was 0.1% in livers perfused with BAL, 9.6% for DMSA, 12.3% for DMPS, and 13.3% for BAPSA, respectively. Except BAL, all compounds and most effectively BAPSA increased biliary excretion of arsenic. This indicates that excretion of arsenic which normally is mainly renal is shifted towards faecal excretion by the dithiols.

Effect of glucose treatment on carbohydrate content in various organs in mice after acute As2O3 poisoning.

Glucose treatment improved survival and symptoms in mice poisoned with As2O3. In order to get more insight into the mechanisms involved, postmortum changes in glucose and glycogen content of various organs and pathology were investigated in mice acutely poisoned with As2O3 and treated with glucose. Forty mice each received 12.9 mg As2O3/kg sc as a single injection. The first group of 10 mice had no further treatment. Fifteen minutes after the As2O3 injection and every 2 h thereafter, the second group (10 mice) received saline and the third group (10 mice) received 5% glucose ip. Groups 4 and 5 (5 mice each) received either saline or glucose only. The injection volume in all groups was 10 microliters/g mouse. Group 6 (5 mice) had no treatment whatsoever. Immediately after death brain, muscle and kidneys were prepared for the enzymatic determination of glucose and glycogen. Samples of the brain, muscle, kidneys, liver, small intestine, colon and spleen were taken for microscopic examination. Independent of the therapeutic procedure, decreases in the glycogen in livers and increases in fat in livers and muscles were observed in mice which died. All mice which died showed heavy leucocytes disruptions, increased fat, and decreased glycogen in the spleen. Intrafolliculary disruptions of leucocytes in the small intestine and colon, as well as patchy hyperemias and hemorrhagic spots in the papilla of the kidneys, were observed in non-survivor mice. Decreased glucose and glycogen was in the brains of non-survivor mice; no differences in glucose and glycogen were found in brains of the mice which survived.(ABSTRACT TRUNCATED AT 250 WORDS)

Pyruvate and lactate metabolism in livers of guinea pigs perfused with chelating agents after repeated treatment with As2O3.

The relative effectiveness of British Anti-Lewisite (BAL), dimercaptopropanesulfonic acid (DMPS), dimercaptosuccinic acid (DMSA), and a new metal binding agent 2,3-bis(acetylthio)propanesulfonamide (BAPSA) was compared by determining their effect on pyruvate metabolism in perfused livers of guinea pigs after repeated treatment with As2O3. Guinea pigs received As2O3, 2.5 mg/kg s.c. twice daily on 5 consecutive days (total dose 25 mg/kg). Sixteen hours after the last dose the livers were perfused (2.5 ml/min/g liver) with Krebs-Henseleit buffer and glucose (10 mmol/l) as substrate for 80 min. After 50 min of perfusion 0.1 or 0.7 mmol/l BAL, DMPS, DMSA, or BAPSA were added to the perfusate for 30 min. Samples of the effluent were collected every 10 min; lactate and pyruvate were determined enzymatically. As compared to controls, a significant decrease in the pyruvate and lactate efflux was observed in perfused livers of guinea pigs treated with As2O3. After influx of BAL (0.1 mmol/l), DMSA (0.7 mmol/l), and BAPSA (0.1 and 0.7 mmol/l) respectively, the pyruvate and lactate efflux and the oxygen consumption (exception BAL 0.1 mmol/l) increased and reached control values without arsenic treatment. On the other hand, the pyruvate and lactate efflux and the oxygen consumption was further significantly decreased after influx of 0.7 mmol/l BAL.

Effect of chelating agents on biliary excretion of arsenic in perfused livers of guinea pigs pretreated with As2O3.

The effect of the dithiols British Anti-Lewisite (Bal), dimercapto-propanesulfonic acid (DMPS), dimercaptosuccinic acid (DMSA) and a new metal binding agent 2,3-bis-(acetylthio)-propanesulfonamide (BAPSA) on the biliary excretion of arsenic in perfused livers of guinea pigs pretreated with As2O3 was investigated. Guinea pigs received As2O3, 2.5 mg/kg sc twice daily for 5 consecutive days. Sixteen hours after the last dose the livers were perfused (35 ml/min) with Krebs-Henseleit buffer with glucose for 80 min. After 50 min of perfusion 0.1 mmol/L or 0.7 mmol/L BAL, DMSA, DMPS, or BAPSA were added to the perfusate and arsenic elimination in the bile and effusate was measured. The total arsenic excretion in control livers between the 50th and 80th min was 6.1% of the total arsenic liver content. After antidote addition (0.1 mmol/L) the excretion increased to 7.9% (DMSA), 9.2% (BAL), 23.9% (BAPSA), and 27.1% (DMPS), respectively. After 0.7 mmol/L of antidote the excretion of arsenic was found to be 19.3% (DMSA), 19.9% (DMSA), 24.0% (BAL), and 43.3% (BAPSA), respectively. The increase resulted mainly from increased biliary excretion. In these experiments BAPSA was significantly more effective in the overall elimination of arsenic than DMSA, DMPS, and BAL. The treatment with chelating agents may cause a substantial shift to fecal elimination by the increase in biliary excretion (BAL less than DMSA less than DMPS less than BAPSA). From the therapeutic view the shift to fecal elimination may have the advantage that the amount of the toxicant which passes the kidney is reduced and thereby also the portion which might be harmful for the organ.

Effect of glucose in mice after acute experimental poisoning with arsenic trioxide (As2O3).

Carbohydrate depletion (glucose and glycogen) was reported to be a major problem in acute arsenic poisoning. In the present paper the effectiveness of glucose substitution was investigated in mice after acute experimental poisoning with As2O3. Four groups of ten mice each received As2O3, 12.9 mg/kg, s.c. After the injection the first group remained without further treatment, the second received saline every 2 h, the third 5% glucose, and the fourth 5% glucose +0.12 IE insulin/kg i.p. Groups 5 and 6, five mice each, received either saline or glucose only. Group 7, five mice, remained without any treatment. Immediately after death the livers were removed for the enzymatic determination of glucose and glycogen. Mice receiving As2O3 only died within 22 h. The mean survival time was 12.4 h. In mice receiving As2O3 and after that saline, glucose, or glucose + insulin, an increase in the survival time to 30.8, 40.7, and 43.6 h, respectively, was observed. All mice which died showed a significant decrease in the liver glucose and glycogen content, compared to control animals. In livers of survivors, the glucose and glycogen content was not different to the control groups. The data support the assumption that carbohydrate depletion is an important factor in arsenic toxicity, and its substitution should be considered in the treatment of arsenic poisoning.