Studies on the distribution and co valent binding of 1,1-dichloroethylene in the mouse: Effect of various pretreatments on covalent binding in vivo
Abstract
The distribution and covalent binding of a single dose of [1, 2-14C]1, 1-dichloroethylene (DCE; 125 mg/kg, i.p.) was studied in male C57B1/6N mice. Total radioactivity was distributed in whole homogenates of all tissues studied, with peak levels occurring within 6 hr. Covalent binding of radioactive material peaked at 6–12 hr in all tissues, and highest levels were found in kidney, liver, and lung with smaller amounts in skeletal muscle, heart, spleen, and gut. Covalent binding in kidney, liver, and lung fell to 50% of peak levels in about 4 days. Between 12 hr and 4 days after DCE administration, 70–100% of total radioactivity present in homogenates of kidney, liver, and lung was covalently bound. The three tissues showed a similar spread in total radioactivity in subcellular fractions 24 hr after exposure to DCE; most of the radioactivity was covalently bound (60–100%) and distributed fairly uniformly with a slight tendency to concentrate in the mitochondrial fraction. Phenobarbital (PB) and 3-methylcholanthrene (3-MC) pretreatments increased the covalent binding in the liver and lung but had no effect in the kidney. Piperonyl butoxide and SKF-525A decreased the covalent binding in liver and lung, but the latter increased binding in the kidney while the former decreased it. Diethylmaleate administration increased the covalent binding (2- to 3-fold) in all three tissues as well as increasing lethal toxicity. These results are consistent with the view that DCE is metabolized to some reactive intermediate(s) which may be detoxified by conjugation with glutathione
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Cited by (26)
Halogenated Hydrocarbons
2010, Comprehensive Toxicology, Second EditionHalogenated hydrocarbons represent a large group of aromatic and aliphatic compounds with diverse industrial, agricultural, medical, and public health applications. Aliphatic halogenated hydrocarbons comprise many haloalkanes, haloalkenes, and haloalkynes which are released into the environment or detected in drinking water to which general public are exposed by various routes. These halogenated hydrocarbons can induce toxicity after biotransformation to multiple organs, especially kidney in experimental animals, and is a concern about the potential human health. The objective of this chapter is to review knowledge on the renal toxicology of representative haloalkanes and haloalkenes, the biochemical basis for their kidney selectivity, and, when possible, to correlate species- and sex-related differences in metabolism and nephrotoxicity.
Reaction of glutathione with the electrophilic metabolites of 1,1-dichloroethylene
1995, Chemico-Biological Interactions1,1-Dichloroethylene (DCE) requires cytochrome P450-catalyzed bioactivation to electrophilic metabolites (1,1-dichloroethylene oxide, 2-chloroacetyl chloride and 2,2-dichloroacetaldehyde) to exert its cytotoxic effects. In this investigation, we examined the reactions of these metabolites with glutathione by spectroscopic and Chromatographic techniques. In view of the extreme reactivity of 2-chloroacetyl chloride, primary reactions are likely to include alkylation of cytochrome P450, conjugation with GSH to give S-(2-chloroacetyl)-glutathione, or hydrolysis to give 2-chloroacetic acid. Our results showed conjugation of GSH with 1,1-dichloroethylene oxide, through formation of the mono- and di-glutathione adducts, 2-S-glutathionyl acetate and 2-(S-glutathionyl) acetyl glutathione, respectively. The observed equilibrium constant between the hydrate of 2,2-dichloroacetaldehyde and S-(2,2-dichloro-1-hydroxy)ethylglutathione was estimated from 1H-NMR experiments to be 14 ± 2 M−1. Thus, 2,2-dichloroacetaldehyde is unlikely to make a significant contribution to GSH depletion as GSH concentrations above normal physiological levels would be necessary to form significant amounts of S-(2,2-dichloro-1-hydroxy)ethylglutathione. We also compared the formation of the glutathione conjugates in rat and mouse liver microsomes using 14C-DCE. The results demonstrated a species difference; the total metabolite production was 6-fold higher in microsomes from mice, compared with samples from rat. Production of DCE metabolites in hepatic microsomes from acetone-pretreated mice was 3-fold higher than those from untreated mice suggesting a role for P450 2E1 in DCE bioactivation. These results indicate that the epoxide is the major metabolite of DCE that is responsible for GSH depletion, suggesting that it may be involved in the hepatotoxicity evoked by DCE. Furthermore, this metabolite is formed to a greater extent in mouse than in rat liver microsomes and this difference may underlie the enhanced susceptibility found in the former species.
Single exposures of mice to methylene chloride (MC) cause vacuolation and necrosis of the bronchiolar Clara cells which subsequently recover normal morphology on continued exposure. Both cytochrome P-450 (CYP)- and glutathione S-transferase (GST)-dependent metabolism of MC are known to occur. The current studies have investigated the metabolism of MC in mouse lung using inhibitors of both GST and CYP-dependent routes of metabolism, the consequences of metabolic inhibition on the Clara cell vacuolation, and any changes in cell proliferation, assessed in vitro, in Clara cells cultured from exposed individuals. Vacuolated bronchiolar cells were seen in mice exposed to 2000 and 4000 ppm MC but were not seen at lower concentrations, while addition of the CYP inhibitor, piperonyl butoxide, significantly reduced the bronchiolar cell vacuolation seen following exposure to 2000 ppm MC. Treatment of mice with the glutathione depletor, buthionine sulphoximine, had no effect on the number of vacuolated bronchiolar cells following MC. Exposure of mice to 1000 ppm MC and above for 6 h caused a burst of DNA synthesis in bronchiolar Clara cells cultured in vitro from the lungs of exposed animals. The results suggest that the Clara cell vacuolation following MC exposure is mediated via CYP metabolism, that depression of the CYP metabolic pathway occurs following exposure, and that Clara cell vacuolation may have a priming role in stimulating cell proliferation in the unaffected cell population.
1,1-Dichloroethylene hepatotoxicity: Hypothyroidism decreases metabolism and covalent binding but not injury in the rat
1991, ToxicologyOur objective was to determine if the previously reported protective effect of hypothyroidism against 1,1-dichloroethylene hepatotoxicity was associated with a change in distribution and covalent binding. Sprague-Dawley male rats were made hypothyroid (HypoT) by surgical thyroidectomy 2 weeks prior to studies and compared to euthyroid (EuT) rats. Hypothyroidism decreased body weights and liver to body weight ratios while mitochondrial non-protein sulfhydryl groups and cytosolic alcohol dehydrogenase activities were increased by 50%. Rats received a single oral dose of 100 mg [14C]1,1-dichloroethylene (DCE)/kg in mineral oil and were killed at 2, 4, 12 or 24 h; controls received mineral oil only. More rapid liver injury, as measured by serum alanine aminotransferase activity and histology, was present at 2 and 4 h after DCE in HypoT than EuT rats, but a similar magnitude of injury was evident at 12 and 24 h. DCE decreased liver non-protein sulfhydryl groups to a comparable extent in HypoT and EuT rats. Cytosolic glutathione S-transferase and alcohol dehydrogenase activities were decreased only in HypoT rats after DCE. HypoT rats excreted ∼30% less total [14C]DCE-derived label in urine and their livers. kidneys and lungs consistently contained slightly less covalently bound [14C]DCE-derived label. In contrast, between 1 and 4 h after DCE, greater amounts of acid-soluble and acid-precipitable [14C]DCE-derived label were recovered in red blood cells of HypoT rats. Our results indicate that hypothyroidism did not protect against oral DCE hepatotoxicity but was associated with a more rapid injury at early time. Concurrently, hypothyroidism was found to change the fate of [14C]DCE with higher amounts of 14C-label recovered at early times in red blood cells while less 14C-label was excreted in urine and bound to liver.
Potentiation of 1,1-dichloroethylene hepatotoxicity: Comparative effects of hyperthyroidism and fasting
1988, Toxicology and Applied PharmacologyThe responses of fed, fasted, and hyperthyroid (T4) Sprague-Dawley male rats to 50 mg 1,1-dichloroethylene (1,1-DCE)/kg were compared. Hyperthyroid rats received three sc injections of thyroxine (100 μg/100 g) at 48-hr intervals; all other rats were sham-injected. 1,1-DCE was given po in mineral oil 24 hr after the last T4 dose; controls received only mineral oil. Animals were killed at 2, 4, and 8 hr. Liver GSH contents were lowered about 55% by both fasting and T4 while GSH transferase activities were lowered about 20% by fasting and 35% by T4. Only T4 pretreatment lowered alcohol dehydrogenase activities. Liver injury (i.e., serum glutamate pyruvate transaminase, histology) after 1,1-DCE was minimal in fed rats, moderate in fasted rats, and intermediate in T4 rats. Fasted rats showed a more pronounced depletion of liver GSH after 1,1-DCE than T4 rats and only in fasted rats did the toxicant decrease activities of the detoxification enzymes. Hypoglycemia after 1,1-DCE occurred in fed rats, but more rapidly in T4 rats. In contrast, fasted rats unexpectedly became hyperglycemic after the toxicant. Patterns of body temperature change after the toxicant, which might be due to its metabolites, were dissimilar. Hypothermia was not observed in fed rats, was only transiently evident in T4 rats, but occurred rapidly within 1 hr in fasted rats and steadily became more severe. The dissimilar patterns of liver enzyme and body temperature and serum glucose change after the toxicant in the three groups are indicative of different pathways of injury potentiation by fasting and hyperthyroidism.
Municipal wastewater contamination in the Southern California Bight. Part II. Cytosolic distribution of contaminants and biochemical effects in fish livers
1987, Marine Environmental ResearchThe objective of this study was to examine the cytosolic distribution of metals and oxygenated organic metabolites (MTBs), and biochemical effects, in livers of fish collected from both highly contaminated and less contaminated southern California coastal sites. Cytosolic extracts were separated by Sephadex G-75 column chromatography into high molecular weight (> 20 000 daltons) enzyme-containing (ENZ) pools, medium molecular weight (3000–20000 daltons) metallothionein- or metallothionein-like-containing (MT) pools, and low molecular weight (< 3000 daltons) glutathione-containing (GSH) pools.
Concentrations of Cd, Cu and Zn were frequently lower in cytosolic pools of longspine combfish, yellowchin sculpin, and California tonguefish from highly contaminated Palos Verdes (PV) relative to those from less contaminated Santa Monica Bay (SMB) despite much higher concentrations of these metals in sediments at PV. Patterns of cytosolic metal distribution differed more between metals than between species or sampling locations. Most Cd, Cu and Zn occurred in the MT pools of these three species, with the exception of Zn in California tonguefish which occurred predominately in the ENZ pool. In all three species, ENZ-Cu showed positive slopes when regressed against total cytosolic Cu, while ENZ-Cd showed no significant slopes when regressed against total cytosolic Cd. Patterns for Zn were the least consistent among species, with higher ENZ-Zn slopes occurring in fish livers with lower cytosolic Zn concentrations.
The largest portion of DDT and PCB oxygenated MTBs occurred in GSH pools of scorpionfish livers from PV or less contaminated Cortes Bank (CB). Concentrations of MTBs in ENZ- and MT-pools of CB scorpionfish livers showed positive slopes when regressed against total cytosolic- and GSH-MTBs.
Positive slopes for regressions of ENZ-Cu, -Zn and -MTBs against total cytosolic concentrations are consistent with the model of an equilibrium-dependent exchange of these among cytosolic pools.
The lower metal concentrations, higher glutathione concentrations, and higher catalase activities found in fish from PV relative to those from SMB are in accordance with effects known to result from exposure to organic contaminants.