Effect of dose on the disposition of methoxyethanol, ethoxyethanol, and butoxyethanol administered dermally to male F344/N rats

Ethylene oxide derived glycol ethers: A review of the alkyl glycol ethers potential to cause endocrine disruption

The 'ethylene glycol ethers' (EGE) are a broad family of solvents and hydraulic fluids produced through the reaction of ethylene oxide and a monoalcohol. Certain EGE derived from methanol and ethanol are well known to cause toxicity to the testes and fetotoxicity and that this is caused by the common metabolites methoxy and ethoxyacetic acid, respectively. There have been numerous published claims that EGE fall into the category of 'endocrine disruptors' often without substantiated evidence. This review systematically evaluates all of the available and relevant in vitro and in vivo data across this family of substances using an approach based around the EFSA/ECHA 2018 guidance for the identification of endocrine disruptors. The conclusion reached is that there is no significant evidence to show that EGE target any endocrine organs or perturb endocrine pathways and that any toxicity that is seen occurs by non-endocrine modes of action.

Disposition and metabolism of ethylene glycol 2-ethylhexyl ether in Sprague Dawley rats, B6C3F1/N mice, and in vitro in rat hepatocytes

Ethylene glycol 2-ethylhexyl ether (EGEHE) is a solvent used in a variety of applications.We report disposition and metabolism of EGEHE following a single gavage or dermal administration of 50, 150 or 500 mg/kg [¹⁴C]EGEHE in rats and mice and in vitro in rat hepatocytes.EGEHE was cleared rapidly in rat hepatocytes (half-life ∼4 min) with no sex difference.EGEHE was well- and moderately absorbed following oral administration (rats: 80-96%, mice: 91-95%) and dermal application (rats: 25-37%, mice: 22-24%), respectively, and rapidly excreted in urine.[¹⁴C]EGEHE-derived radioactivity was distributed to tissues (oral: 2.3-7.2%, dermal: 0.7-2.2%) with liver and kidney containing the highest levels in both species.EGEHE was extensively metabolised with little to no parent detected in urine. The alkoxyacetic acid metabolite, which has previously been shown to mediate toxicities of other shorter-chain ethylene glycol ethers, was not detected.There were no apparent dose, species or sex differences in disposition and metabolism of EGEHE, except that the exhaled volatile compounds were greater in mice (19-20%) compared with rats (<2%).These studies address a critical gap in the scientific literature and provide data that will inform future studies designed to evaluate toxicity of EGEHE.

The urinary metabolic profile of diethylene glycol methyl ether and triethylene glycol methyl ether in Sprague-Dawley rats and the role of the metabolite methoxyacetic acid in their toxicity

Ethylene glycol ethers are a well-known series of solvents and hydraulic fluids derived from the reaction of ethylene oxide and monoalcohols. Use of methanol as the alcohol results in a series of mono, di and triethylene glycol methyl ethers. The first in the series, monoethylene glycol methyl ether (EGME or 2-methoxyethanol) is well characterised and metabolises in vivo to methoxyacetic acid (MAA), a known reproductive toxicant. Metabolism data is not available for the di and triethylene glycol ethers (DEGME and TEGME respectively). This study evaluated the metabolism of these two substances in male rats following single oral gavage doses of 500, 1000 and 2000 mg/kg for DEGME and 1000 mg/kg for TEGME. As for EGME, the dominant metabolite of each was the acid metabolite derived by oxidation of the terminal hydroxyl group. Elimination of these metabolites was rapid, with half-lives <4 h for each one. Both substances were also found to produce small amounts of MAA (~0.5% for TEGME and ~1.1% for DEGME at doses of 1000 mg/kg) through cleavage of the ether groups in the molecules. These small amounts of MAA produced can explain the effects seen at high doses in reproductive studies using DEGME and TEGME.

Hematological effects of exposure to mixtures of selected ethylene glycol alkyl ethers in rats

Exposure to various ethylene glycol monoalkyl ethers (EGAEs) is known to result in hemolytic effect caused by their metabolites, appropriate alkoxyacetic acids, generated via both alcohol dehydrogenase and aldehyde dehydrogenase. It has been shown in many studies that administration of single doses of EGAEs to rats lead to dose- and time-dependent hemolytic anemia. The repeated exposure to isopropoxyethanol (IPE), and butoxyethanol (BE), contrary to methoxyethanol (ME) and ethoxyethanol (EE), resulted in significantly less pronounced hematological changes. While the majority of hematological effects were dramatic at the beginning of the exposure, later these changes clearly regressed despite continued weekly exposure to these ethers. The gradual recovery from the hemolytic anemia may be associated with tolerance development to the hemolytic effect of IPE and BE. ME demonstrated high hematotoxicity, which increased progressively and reached a maximum at the end of 4 week exposure, whereas EE revealed moderate hematological effects. It might be suspected that ME and EE may modified of IPE hemolytic activity in rats simultaneously treated with these compounds. In the rats co-exposed to IPE and ME subcutaneously at a relatively low doses of 0.75 mM + 0.75 mM for 4 weeks, a significantly less pronounced hematological changes at the beginning of the exposure in comparison with animals treated with IPE (0.75 mM) alone were observed. At the later period, i.e., at the end of 4 weeks exposure, the hematological alterations in the same animals were markedly pronounced and progressively elevated with exposure time, except for mean corpuscular volume (MCV) values, which were significantly lower in comparison with IPE group. ME at the higher dose of 1.25 mM/kg and EE at both doses of 0.75 and 1.25 mM/kg did not modify the hematotoxicity of IPE (at doses of 0.75 mM and 1.25 mM) at the beginning of the exposure, whereas increased its harmful effects at the end of the treatment. The amelioration in the majority of the hematological parameters at the beginning of the exposure may be caused by inhibitory effect of ME on IPE metabolism. On the contrary, an accumulation of the methoxyacetic acid and ethoxyacetic acid, toxic metabolites of ME and EE, respectively, and no tolerance development to the hemolytic effect of these two chemicals may be responsible for elevated hematological alterations at the end of the exposure.

Diethylene glycol monomethyl ether, ethylene glycol monomethyl ether and the metabolite, 2-methoxyacetic acid affect in vitro chondrogenesis

Diethylene glycol monomethyl ether (DEGME), ethylene glycol monomethyl ether (EGME) and their common metabolite, methoxyacetic acid (MAA) have been associated with adverse reproductive effects. The objective of this research is to investigate the effects of DEGME, EGME and MAA on in vitro chondrogenesis and the mechanisms by which these effects occur. Micromass cultures were exposed to DEGME, EGME or MAA for 5 days and proteoglycan abundance and cell proliferation determined. Longer-term 9- and 14-day cultures were exposed to MAA and apoptosis analyzed. All three chemicals decreased proteoglycan abundance and cell proliferation at the highest dose tested (100 microL/mL). However, only MAA showed a dose-dependent effect for both parameters at 0.01, 10, and 100 microL/mL. Furthermore, micromass cultures show an increase in apoptotic cells which when treated with MAA suggest that cell death could result from induced apoptosis. These results suggest that effects of DEGME and EGME are the result of generalized toxicity, but their metabolite MAA induces mitochondrial-mediated apoptosis during in vitro chondrogenesis.

Determination of age and gender differences in biochemical processes affecting the disposition of 2-butoxyethanol and its metabolites in mice and rats to improve PBPK modeling

2-Butoxyethanol (BE) is the most widely used glycol ether solvent. BEs major metabolite, butoxyacetic acid (BAA), causes hemolysis with significant species differences in sensitivity. Several PBPK models have been developed over the past two decades to describe the disposition of BE and BAA in male rats and humans to refine health risk assessments. More recent efforts by Lee et al. [Lee, K.M., Dill, J.A., Chou, B.J., Roycroft, J.H., 1998. Physiologically based pharmacokinetic model for chronic inhalation of 2-butoxyethanol. Toxicol. Appl. Pharmacol. 153, 211-226] to describe the kinetics of BE and BAA in the National Toxicology Program (NTP) chronic inhalation studies required the use of several assumptions to extrapolate model parameters from earlier PBPK models developed for young male rats to include female F344 and both sexes of B6C3F1 mice and the effects of aging. To replace these assumptions, studies were conducted to determine the impact of age, gender and species on the metabolism of BE, and the tissue partitioning, renal acid transport and plasma protein binding of BAA. In the current study, the Lee et al. PBPK model was updated and expanded to include the further metabolism of BAA and the salivary excretion of BE and BAA which may contribute to the forestomach irritation observed in mice in the NTP study. The revised model predicted that peak blood concentrations of BAA achieved following 6 h inhalation exposures are greatest in young adult female rats at concentrations up to 300 ppm. This is not the case predicted for old (> or =18 months) animals, where peak blood concentrations of BAA in male and female mice were similar to or greater than female rats. The revised model serves as a quantitative tool for integrating an extensive pharmacokinetic and mechanistic database into a format that can readily be used to compare internal dosimetry across dose, route of exposure and species.

Percutaneous penetration and metabolism of 2-butoxyethanol

2-Butoxyethanol (2-BE) is widely used as an industrial solvent, which may result in human dermal exposure within the workplace. This study compares in vivo and in vitro skin absorption of 2-BE using similar application regimes and determines the potential of skin to metabolise this chemical prior to entering the systemic blood circulation. Following topical application of undiluted [1-14C] 2-BE to occluded rat skin in vivo, 28% of the dose was absorbed after 24 h. The major routes of excretion included the urine (19%), expiration as carbon dioxide (6%) and faeces (0.4%) whilst little of the dose remained in the carcass (1.3%). Free 2-BE (0.5%), butoxyacetic acid (8%), glucuronide conjugate (3%), sulphate conjugates (0.7%) and ethylene glycol (0.6%) were detected in urine. Permeation rates of 2-BE through unoccluded rat dermatomed skin (16%) were greater than rat whole skin (8%) whilst absorption through human dermatomed skin (4%) was lower than the rat. Absorption of undiluted 2-BE through occluded rat dermatomed skin in vitro (18%) most accurately predicted absorption through rat skin in vivo. However, 2-BE absorption (23%) was enhanced by application in methanol. Distribution analysis and microautoradiography demonstrated the lack of 2-BE accumulation within the skin in vitro or in vivo. This was reflected in the absence of first pass metabolism of 2-BE during percutaneous penetration through viable human or rat skin in vitro or rat skin in vivo, despite rat skin cytosol having the potential to metabolise 2-BE. In conclusion, the in vitro system provided a reasonable estimate of dermal absorption in vivo for the rat. Therefore, by extrapolation of the comparative in vitro data for human and rat skin in vitro, dermal absorption of 2-BE in man was about one-fifth of that in the rat. However, the rapid penetration through skin in vitro prevented local metabolism and systemic exposure after skin contact with 2-BE in vivo was likely to be to the parent compound. Thus, in vitro skin systems can be used to model dermal absorption of volatile glycol ethers, to predict how much compound enters the circulation and allows the toxicologist to evaluate the body burden of a chemical and potential systemic toxicity.

Final report on the safety assessment of ethoxyethanol and ethoxyethanol acetate

Ethoxyethanol is an ether alcohol described as a solvent and viscosity-decreasing agent for use in cosmetics. Ethoxyethanol Acetate is the ester of Ethoxyethanol and acetic acid described as a solvent for use in cosmetics. Although these ingredients have been used in the past, neither ingredient is in current use. Ethoxyethanol is produced by reacting ethylene oxide with ethyl alcohol. Ethoxyethanol Acetate is produced via an esterification of Ethoxyethanol and acetic acid, acetic acid anhydride, or acetic chloride. Ethoxyethanol is metabolized to ethoxyacetaldehyde, which is further metabolized to ethoxyacetic acid, which is also a metabolite of Ethoxyethanol Acetate. Low to moderate acute inhalation toxicity is seen in animals studies. Acute oral toxicity studies in several species reported kidney damage, including extreme tubular degeneration. Kidney damage was also seen in acute dermal toxicity studies in rats and rabbits. Minor liver and kidney damage was also seen in short-term studies of rats injected subcutaneously with Ethoxyethanol, but was absent in dogs dosed intravenously. Mixed toxicity results were also seen in subchronic tests in mice and rats. Ethoxyethanol and Ethoxyethanol Acetate were mild to moderate eye irritants in rabbits; mild skin irritants in rabbits, and nonsensitizing in guinea pigs. Most genotoxicity tests were negative, but chromosome aberrations and sister-chromatid exchanges were among the positive results seen. Numerous reproductive and developmental toxicity studies, across several species, involving various routes of administration, indicate that Ethoxyethanol and Ethoxyethanol Acetate are reproductive toxicants and teratogens. Mild anemia was reported in individuals exposed occupationally to Ethoxyethanol, which resolved when the chemical was not used. Reproductive effects have been noted in males exposed occupationally to Ethoxyethanol. Although there are insufficient data to determine the potential carcinogenic effects of Ethoxyethanol or Ethoxyethanol Acetate, there is evidence that these chemicals are absorbed across human skin and that they are reproductive and developmental toxicants via dermal exposure. Therefore, these ingredients are unsafe for use in cosmetic formulations.

Percutaneous penetration and metabolism of 2-ethoxyethanol

Percutaneous absorption and cutaneous metabolism of 2-ethoxyethanol were assessed in vivo and with an in vitro flow-through diffusion system. Topical application of undiluted (14)C-ethoxyethanol to occluded rat skin in vivo resulted in 25% of the dose being absorbed after 24 h. The major routes of excretion included the urine (15%), expiration as carbon dioxide (6%), and feces (1.2%), while little of the dose remained in the carcass (1.3%). Free ethoxyethanol, ethoxyacetic acid, and glycine conjugate were detected in urine. Permeation rates of ethoxyethanol through unoccluded rat split skin (20%) were greater than rat whole skin (11%), while absorption through human split skin (8%) was lower than the rat. Absorption of undiluted ethoxyethanol through occluded rat split skin in vitro (22%) most accurately predicted absorption through rat skin in vivo. However, ethoxyethanol absorption (29%) was enhanced by application in methanol. First pass metabolism of ethoxyethanol was not detected during percutaneous penetration through viable human or rat skin in vitro or rat skin in vivo. However, rat skin cytosol had the potential to metabolize ethoxyethanol, suggesting that the rapid penetration through skin in vivo prevented metabolism and that systemic exposure after skin contact with 2-ethoxyethanol is likely to be to the parent compound. In conclusion, the in vitro system provided a reasonable estimate of dermal absorption for the rat in vivo and comparison of human and rat skin in vitro indicated 2-ethoxyethanol absorption in humans is about one-third of that in the rat.

Suppression of the contact hypersensitivity response following topical exposure to 2-butoxyethanol in female BALB/c mice

The effects of route of exposure, time of exposure and metabolism of 2-butoxyethanol (BE) on the contact hypersensitivity response (CHR) were evaluated in female BALB/c mice. Mice were either orally exposed to 50, 150 or 400 mg BE/kg or topically exposed to 0.25, 1.0, 4.0 or 16.0 mg BE on the ear and the oxazolone (OXA)-induced CHR evaluated by measuring ear thickness before and after OXA challenge. While no modulation was observed following oral exposure to BE, topical exposure resulted in a significant decrease in the CHR. Application of 4.0 mg BE in 4:1 acetone and olive oil (AOO) vehicle at the time of sensitization, challenge or both, decreased the CHR by 18%, 18% and 22%, respectively. A time course study of the effects of topical exposure to 4.0 mg BE/ear during the challenge phase of the CHR revealed that BE must be applied at the time of OXA challenge to significantly reduce the ear swelling response. In order to determine if metabolism of topically applied BE was required for suppression of the CHR, butoxyacetic acid (BAA), the primary metabolite of BE, was applied to the ear immediately following OXA challenge. No topical dose of BAA (2.0,4.0 and 8.0 mg BAA/ear) administered in this study altered the CHR. Blocking the metabolism of BE by oral administration of 4-methylpyrazole (MP), further reduced OXA-induced ear swelling when compared to mice exposed to BE without MP treatment. Taken together, these studies indicated that suppression of the CHR in mice following topical exposure to this glycol ether was due to the activity of BE itself and was not dependent on metabolic activation of the compound. Further studies were undertaken to identify a potential mechanism of BE-induced reduction of the CHR. Epidermal cells from untreated BALB/c mice were isolated and exposed to BE in vitro (10(-12), 10(-10), 10(-8), 10(-6) and l0(-4) M BE). In vitro exposure to BE at these concentrations did not significantly affect expression of MHC class II surface protein or protein synthesis in epidermal Langerhans cells, failing to provide in vitro evidence that BE-associated suppression of the CHR is associated with a reduction in MHC class II expression.

Topical exposure to 2-butoxyethanol alters immune responses in female BALB/c mice

Effects on immune parameters following topical exposure to 2-butoxyethanol (BE) in mice are reported in the present study. The objective was to determine whether subacute topical exposure to BE can modulate functional immune responses and/or nonspecific immune parameters such as lymphoid organ weight and cellularity. Female BALB/c mice were topically exposed to vehicle or BE at concentrations of 100, 500, 1,000, and 1,500 mg BE/kg/day for 4 consecutive days. Assessment of immune parameters began 24 hours after the final dose. No effects were observed at any of the BE concentrations on thymus cellularity or thymus to body weight ratio. A significant increase in spleen cellularity and spleen to body weight ratio was observed at 1,500 mg BE/kg/day. Topical BE exposure significantly reduced the splenic T cell proliferative response to concanavalin A (Con A) and the mixed lymphocyte response (MLR) to allogeneic antigen. No significant effect was observed in the splenic B cell proliferative response to lipopolysaccharide (LPS), nor was there an effect on the in vitro primary antibody response to sheep red blood cells (SRBCs). No significant alteration occurred in either splenocyte cytotoxic T lymphocyte (CTL) activity or natural killer (NK) cell activity following topical BE exposure. This study suggests that topical exposure to BE may suppress some aspects of T cell immunity but does not affect B cell immunity.

A toxicokinetic study of inhaled ethylene glycol monomethyl ether (2-ME) and validation of a physiologically based pharmacokinetic model for the pregnant rat and human

Exposures to sufficiently high doses of ethylene glycol monomethyl ether (2-methoxyethanol, 2-ME) have been found to produce developmental effects in rodents and nonhuman primates. The acetic acid metabolite of 2-ME, 2-methoxyacetic acid (2-MAA), is the likely toxicant, and, as such, an understanding of the kinetics of 2-MAA is important when assessing the potential risks to humans associated with 2-ME. A previously described physiologically based pharmacokinetic (PBPK) model of 2-ME/2-MAA kinetics for rats exposed via oral or iv administration was extended and validated to inhalation exposures. Pregnant Sprague-Dawley rats were exposed for 5 days (gestation days 11-15), 6 h/day, to 2-ME vapor at 10 and 50 ppm. Validation consisted of comparing model output to maternal blood and fetal 2-ME and 2-MAA concentrations during and following 5 days of exposure (gestation days 11-15). These concentrations correspond to a known no observed effect level (NOEL) and a lowest observed effect level (LOEL) for developmental effects in rats. The rat PBPK model for 2-ME/2-MAA was scaled to humans and the model (without the pregnancy component) was used to predict data collected by other investigators on the kinetics of 2-MAA excretion in urine following exposures to 2-ME in human volunteers. The partially validated human model (with the pregnancy component) was used to predict equivalent human exposure concentrations based on 2-MAA dose measures (maximum blood concentration, C(max), and average daily area under the 2-MAA blood concentration curve, AUC, during pregnancy) that correspond to the concentrations measured at the rat NOEL and LOEL exposure concentrations. Using traditional PBPK scale-up techniques, it was calculated that pregnant women exposed for 8 h/day, 5 days/week, for the duration of pregnancy would need to be exposed to 12 or 60 ppm 2-ME to produce maternal 2-MAA blood concentrations (C(max) or average daily AUC) equivalent to those in rats exposed to the NOEL (10 ppm) or LOEL (50 ppm), respectively.

A toxicokinetic study of inhaled ethylene glycol ethyl ether acetate and validation of a physiologically based pharmacokinetic model for rat and human

The solvents ethylene glycol monoethyl ether acetate (EGEEA) and ethylene glycol monoethyl ether (EGEE), at sufficiently high doses, are known to be rodent developmental toxicants, exerting their toxic effects through the action of their metabolite 2-ethoxyacetic acid (2-EAA). Thus risks associated with exposure to these compounds are best evaluated based on a measure of the internal dose of 2-EAA. The goals of the work reported here were to develop physiologically based pharmacokinetic (PBPK) models of EGEEA and EGEE for pregnant rats and humans. These models were used to identify human exposure levels (ppm in air) equivalent to the rat no observed effect level (NOEL) and lowest observed effect level (LOEL) for developmental effects (Hanley et al., 1984). We exposed pregnant Sprague-Dawley rats to concentrations of EGEEA corresponding to the NOEL and LOEL. Maternal blood, urine, and fetal tissue concentrations of EGEE and 2-EAA measured in these experiments were used to validate the rat EGEEA and EGEE models. Data collected by other researchers were used to validate the capabilities of the rodent EGEEA and EGEE models to predict the kinetics in humans. The models for estimating circulating blood concentrations of 2-EAA were considered valid based on the ability of the model to accurately predict 2-EAA concentrations in rat blood, urine, and fetal tissue. The human inhaled concentration equivalent to the rat NOEL for EGEEA (50 ppm) was predicted to be 25 ppm using the maternal blood average daily area under the curve (AUC) and 40 ppm using the maximum concentration achieved in maternal blood (C(max)). The human inhaled concentration equivalent to the rat LOEL for EGEEA (100 ppm) was determined to be 55 ppm using the maternal blood average daily AUC and 80 ppm using the maternal blood C(max).

The role of liver alcohol dehydrogenase isoenzymes in the oxidation of glycolethers in male and female rats

The glycolethers 2-methoxyethanol (2-ME), 2-ethoxyethanol (2-EE), and 2-butoxyethanol (2-BE) are used as solvents and have teratogenic, spermatotoxic, and hematotoxic effects. These glycolethers are oxidized to their corresponding alkoxyacetic acids, probably by alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). This metabolic conversion of the glycolethers is a prerequisite for development of toxicity, as the toxic effects have been shown to be due to the alkoxyacetic acid metabolites. Three isoenzymes of ADH have been detected in rat tissues. The liver contains two of these isoenzymes, ADH-2 and ADH-3. It has also been shown that the activity level of ADH is strongly sex dependent, with higher activity in females than in males. In the present study, we have investigated whether one or both of the ADH isoenzymes in male and female rat livers were able to oxidize 2-ME, 2-EE, and 2-BE and whether one or both of the ADH isoenzymes in male rat liver were able to oxidize 2-pentyloxyethanol and 2-hexyloxyethanol. Our results indicated that only the ADH-3 isoenzyme effectively oxidized the glycolethers in rat liver. Both ADH-2 and ADH-3 were able to oxidize medium chain aliphatic alcohols with a chain length corresponding to the glycolethers. The activity of ADH is higher in female than in male rat liver. However, it was the same ADH isoenzyme (ADH-3) that oxidized the different glycolethers tested in both male and female rat livers, and the substrate specificity was 2-BE > 2-EE > 2-ME.

Gender difference in the elimination of 2-methoxyethanol, methoxyacetic acid and ethoxyacetic acid in rat

1. The elimination of 2-methoxyethanol (2-ME) and its toxic metabolite methoxyacetic acid (MAA) was studied in the male and female rat. We also studied the elimination of ethoxyacetic acid (EAA), the toxic metabolite formed by 2-ethoxyethanol (2-EE). 2. The rate of 2-ME elimination after i.p. injection of 2-ME (150 mg/kg) was significantly higher in the female compared with male. The elimination half-life was estimated to 49 +/- 10 min in the male and 28 +/- 5 min in the female. There was, however, no gender difference in the elimination of MAA after i.p. injection of 2-ME (100 mg/kg), and the elimination of MAA was markedly slower compared with 2-ME. The elimination half-life for MAA was estimated to 12.6 +/- 1.3 h in the male and 14.1 +/- 1.4 in the female. 3. The elimination half-life of EAA after i.p. injections of 100 mg/kg 2-EE was estimated to 7.6 +/- 1.1 h and 7.6 +/- 0.75 h in the male and female rat respectively. There was no gender difference in the elimination of EAA, but the rate of elimination of EAA was significantly higher compared with MAA. 4. Accumulation of the toxic metabolites MAA and EAA following frequent exposures to 2-ME and 2-EE respectively can then occur, and it remains to be determined whether there is a sex-difference in the susceptibility to toxic effects following exposure to 2-ME and 2-EE.

Ethylene glycol poisoning: case report of a record-high level and a review

Ethylene glycol is commonly found in automobile antifreeze and a variety of other commercial products. Ingestion of ethylene glycol, either accidentally or in a suicide attempt, is characterized by severe acidosis, calcium oxalate crystal formation and deposition, and a wide variety of end organ effects that may be fatal. We present a case of a patient who ingested a massive amount of ethylene glycol in a suicide attempt and yet survived with minimal sequelae. A comprehensive review of the literature on the pathology and pathophysiology of ethylene glycol toxicity on each organ system is provided, along with information on diagnosis and current treatment recommendations.

Prediction of the percutaneous penetration and metabolism of dodecyl decaethoxylate in rats using in vitro models

Percutaneous absorption of a lipophilic surfactant, dodecyl decaethoxylate, can be predicted using in vitro models. In vivo, dermal penetration of dodecyl decaethoxylate was found to be 22.9% in 48 h. All of the absorbed dodecyl decaethoxylate in the rat was metabolised and excreted in expired air as carbon dioxide, or in the urine and faeces. Using rat skin mounted in the unoccluded flow-through diffusion cell with MEM as receptor fluid, in vivo absorption was predicted by the percentage of the applied dose recovered in the stratum corneum, epidermis, dermis and receptor fluid at 24 h (25%). Conversely, the penetration of dodecyl decaethoxylate was over-predicted in the unoccluded static diffusion cell using aqueous ethanol (50% v/v) as the receptor fluid where 49.4% recovered in the receptor fluid at 24 h. In vitro models may be used to predict percutaneous absorption and reduce animal use, provided a suitable receptor fluid is used in which the penetrant is soluble. Dermal metabolism of dodecyl decaethoxylate was low and not considered to influence dermal absorption.

Species differences in testicular and hepatic biotransformation of 2-methoxyethanol

Biotransformation of 2-methoxyethanol (2-ME) by alcohol and aldehyde dehydrogenases is an established factor in the toxicity of this useful solvent. Little is known about potential capacity for 2-ME biotransformation by testis or other target tissues. We detected appreciable capacity for 2-ME biotransformation by alcohol dehydrogenase in testes from Sprague-Dawley rats. However, kinetic analysis showed a 6-fold lower affinity for 2-ME by alcohol dehydrogenase of testis compared to liver. 2-ME biotransformation was also detected in testes from Wistar rats and one strain of mice but not in testes from hamsters, guinea pigs, rabbits, dogs, cats or humans. Testes from all these species readily converted the aldehyde metabolite of 2-ME to 2-methoxyacetic acid. Hepatic capacities for 2-ME biotransformation by alcohol dehydrogenase varied from 22 to 2.5 mumol/mg prot/min with a species rank order of: hamsters >> rats = mice > guinea pigs = rabbits. There was no consistent concordance between activities for 2-ME versus ethanol, the prototype substrate for alcohol dehydrogenase, which could reflect substrate preferences of different isozymes. Species differences between rats and hamsters were also found for testicular and hepatic biotransformation of the glycol ethers, 2-ethoxyethanol and 2-butoxyethanol. Although species differences in capacity for 2-ME biotransformation were found, the observations do not provide an explanation for reported species and strain differences in susceptibility to 2-ME toxicity.

Inhalation toxicokinetics of butoxyethanol and its metabolite butoxyacetic acid in the male Sprague-Dawley rat

A total of 16 male Sprague-Dawley rats were continuously exposed to 20 ppm or 100 ppm butoxyethanol (BE) vapor for 1, 2, 3, 4, 6, 8, 10, or 12 days. Urine was collected in 24-h intervals and stored at -70 degrees C. At the end of the exposure the animals were euthanized by decapitation and tissue samples of blood, muscle, liver and were rapidly collected and frozen to -70 degrees C. The samples were later derivatized and analyzed for BE and its major metabolite butoxyacetic acid (BAA) by electron capture gas chromatography. BE and BAA were rapidly distributed to the tissues examined. The concentration of BE in blood was slightly higher, and that of BAA markedly higher than in other tissues, indicating weak (BE) and pronounced (BAA) blood protein binding, respectively. BE was efficiently metabolized and the blood clearance averaged 2.6 l/h per kg, corresponding to a hepatic extraction ratio of about 0.75. The renal clearance of BAA (average 0.53 l/h per kg) corresponded to approximately 15% of the renal blood flow. The kinetics of BE and BAA were linear up to 100 ppm. There were no clear indications of changes in the toxicokinetics, such as metabolic induction or inhibition of metabolism or excretion, during the course of the exposure. The recovery of BAA in urine was 64% of the calculated inhaled amount of BE, on an equimolar basis.

Effect of exposure concentration on the disposition of inhaled butoxyethanol by F344 rats

The glycol ethers are a class of solvents widely used due to their range of vapor pressures and miscibility in aqueous and organic media. Butoxyethanol (BE) causes anemia and lowered hematocrits in rats due to direct hemolysis of red blood cells. Exposure to BE is most likely to occur by dermal contact or by inhalation. In this paper, we report the uptake, metabolism, and excretion of BE following 6-hr exposure at different inhaled concentrations. The uptake and metabolism of BE were essentially linear up to 438 ppm. The majority of the inhaled butoxy-[14C]ethanol was eliminated in the urine with butoxyacetic acid (BAA) being the major urinary metabolite, accompanied by lesser amounts of ethylene glycol and BE glucuronide. A small proportion (5-8%) of the retained BE was exhaled as 14CO2. Most (greater than 80%) of the [14C]BE-derived material in blood was in the plasma. BAA was the major metabolite of BE in plasma. Ratios of ethylene glycol to BAA in plasma were higher than those in urine. The BE-derived 14C in plasma rapidly became associated with the acid-precipitable (protein) fraction, probably due to binding of metabolites to proteins or incorporation of the BE metabolites into the carbon pool. These results indicate that, in rats, overall metabolism of BE to BAA, the hemolytic metabolite, was linearly related to the exposure concentration up to a concentration that caused severe toxicity (438 ppm). Assuming that the toxicity of inhaled BE is directly proportional to the formation of BAA, the toxicity of inhaled BE can be expected to be linearly related to the exposure concentration up to exposure concentrations that cause mortality.