Alkoxyacetic Acids Research Articles

Reactions of Peroxide Products of Ozonolysis of Allyl Ethers/Esters in the АсОН-CH2Cl2 System on Treatment with Semicarbazide Hydrochloride

Background: A one-pot method for the preparation of the corresponding alkoxy acetic acids by low-temperature ozonolysis of allyl ethers/esters followed by treatment with semicarbazide hydrochloride has been suggested. The reaction occurs via formation of acetoxyhydroperoxide, subsequent reduction of which depends on the process temperature and the nature of the starting substrate. Keywords: Allyl esters, olefins, semicarbazide hydrochloride, low-temperature ozonolysis, acetoxyhydroperoxide, intermediate, alkoxy acetic acids.

New method of preparation of alkoxyacetic acids

In this work, we report the results of lowtempera� ture ozonolysis of benzyl and phenyl allyl ethers for the preparation of methyl benzyland phenoxyace� tates. The esters of arylacetic acids were prepared by two methods: in the methanol-methylene chloride system in the presence of alkali at -65°C or in methanol at -78°C followed by the treatment of intermediate per� oxide products with semicarbazide hydrochloride. The ozonolysis of benzyl and phenyl allyl ethers Ia and Ib in the presence of NaOH was found to lead in high yield and selectivity to esters IIa and IIb, respectively. Byproducts formed in small amounts are the corre� sponding alkoxyacetic aldehydes IIIa and IIIb. At the same time, the treatment of primary ozonation prod� ucts (peroxides) with semicarbazide hydrochloride gives a mixture of esters IIa and IIb and acetals IVa and IVb (Table 1).

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

AbstractExposure 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 0.75mM + 0.75mM for 4 weeks, a significantly less pronounced hematological changes at the beginning of the exposure in comparison with animals treated with IPE (0.75mM) 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 1.25mM/kg and EE at both doses of 0.75 and 1.25mM/kg did not modify the hematotoxicity of IPE (at doses of 0.75mM and 1.25mM) 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.

A category approach to predicting the hemolytic effects of ethylene glycol alkyl ethers in repeated-dose toxicity

Categorizing chemicals is an approach with the potential to reduce animal testing for hazard assessment of chemicals. In this study we investigated the category approach for testing the hemolytic effects of ethylene glycol alkyl ethers (EGAEs) for repeated-dose toxicity (RDT). Using mechanistic information on the hemolytic effects of ethylene glycol butyl ether, a toxicologically meaningful category was built on the basis of similarity of metabolism, mode of action and the hemolytic effects of several EGAEs and related chemicals. The developed category was then evaluated for analogs from a different data source. Given all structural information on category chemicals, the category can be finally defined as EGAEs (alkyl chain carbon number: 1-4) and their acetates. Current RDT test data suggest that EGAEs with 3 and 4 alkyl carbons primarily cause hemolytic effects, while EGAEs with 1 and 2 alkyl carbon(s) show toxicity to the testis before demonstrating any hemolytic effects. Hence, the category approach appears to be applicable to hemolytic effects of EGAEs with 3 and 4 alkyl carbons and their acetates to estimate the no observable adverse effect level (NOAEL) for RDT. It consists of three steps: structure-based primary screening of untested chemicals, categorization of compounds that form hemolytic alkoxyacetic acids by predicting how they are metabolized, and finally estimation of hemolytic levels by employing read-across. Our results clearly demonstrate the usefulness of the category approach for predicting the hemolytic effects of untested EGAEs and their acetates in RDT.

Human aldehyde dehydrogenase-catalyzed oxidation of ethylene glycol ether aldehydes

Ethylene glycol ethers (EGEs) are primary alcohols commonly used as solvents in numerous household and industrial products. Exposure to EGEs has been correlated with delayed encephalopathy, metabolic acidosis, sub-fertility and spermatotoxicity in humans. In addition, they also cause teratogenesis, carcinogenesis, hemolysis, etc., in various animal models. Metabolism EGEs parallels ethanol metabolism, i.e., EGEs are first converted to 2-alkoxy acetaldehydes (EGE aldehydes) by alcohol dehydrogenases, and then to alkoxyacetic acids by aldehyde dehydrogenases (ALDHs). The acid metabolite of EGEs is considered responsible for toxicities associated with EGEs. The role of human ALDHs in EGE metabolism is not clear; accordingly, we have investigated the ability of five different human ALDHs (ALDH1A1, ALDH2, ALDH3A1, ALDH5A1 and ALDH9A1) to catalyze the oxidation of various EGE aldehydes. The EGE aldehydes used in this study were synthesized via Swern oxidation. All of the human ALDHs were purified from human cDNA clones over-expressing these enzymes in E. coli. The ALDHs tested, so far, differentially catalyze the oxidation of EGE aldehydes to their corresponding acids ( K m values range from ∼10 μM to ∼20.0 mM). As judged by V max/ K m ratios, short-chain alkyl-group containing EGE aldehydes are oxidized to their acids more efficiently by ALDH2, whereas aryl- and long-chain alkyl-group containing EGE aldehydes are oxidized to their acid more efficiently by ALDH3A1. Given the product of ALDH-catalyzed reaction is toxic, this process should be considered as a bio-activation (toxification) process.

Comparison of the in Vitro Hemolytic Effects Produced by Alkoxyacetic Acids on Human and Rat Erythrocytes

The alkoxyacetic acids (AAAs) are urinary metabolites of alkoxyethanol solvents. It is well documented that these chemicals can cause acute hemolytic anemia in humans and laboratory animals. There are scarce data on the relative hemolytic activity of these acids. Likewise, information is lacking on the relationship between their hemolytic activity and physicochemical properties. The aim of this study was to compare the hemolytic activity of five AAAs in red blood cells (RBCs) derived from donors' blood and male Wistar rats. Moreover, the possible relationship between lipophilic and hemolytic activity of AAAs was also investigated. The RBCs washed in TRIS buffer, pH 7.4, were adjusted to a packed cell volume (PCV) of about 20% and incubated in a water bath at 37 degrees C for 0-3 h in the presence of different concentrations of AAAs. The hemolytic effects, in terms of the changes in RBCs, PCV, mean corpuscular volume (MCV) and free hemoglobin (HGBfree) in incubation medium, were evaluated. Based on the dose-response relationship for RBCs, PCV and MCV, the effective concentration values (EC50) and their 95% confidence intervals (95% CI) were calculated. The octanol-water partition coefficient (log P) and distribution coefficient (log D) of AAAs were computed using PALLAS software. The correlation between log P and log D values for AAAs at pH 7.4 and their EC50 was analyzed. Human RBCs were 1.9-3.1 times more resistant to the hemolytic activity of AAAs than rat erythrocytes. Also, the hemolytic activity of individual AAAs did not differ considerably; the maximum differences ranging from 2.0 to 3.3. The EC50 values of AAAs highly correlated with their log P and log D values. The relatively small differences between the hemolytic effects of AAAs on rat and human erythrocytes may be associated with the strong acidity and relatively similar lipophilicity of these chemicals.

Gas Chromatography Analysis of Urinary Alkoxyacetic Acids as Biomarkers of Exposure to Aliphatic Alkyl Ethers

Analysis of alkoxyacetic acids has received considerable research interest in toxicology because these compounds have been reported as metabolites and biomarkers of exposure to widely used industrial chemicals such as alkyl-substituted ethylene glycols and other aliphatic ethers. This paper describes an improved method for the determination of methoxyacetic acid (MAA), ethoxyacetic acid (EAA), and butoxyacetic acid (BAA) in rat urine. Solid-phase extraction with Bakerbond(T) C18 bonded silica cartridges was successfully employed to isolate the acids from rat urine. The acids were then converted to methyl esters with diazomethane derivatization and analyzed using a gas chromatograph (GC) equipped with a mass spectrometry (MS) and a GC with flame ionization detector (FID). Employing GC-MS under selected ion monitoring detection, the lowest detection concentrations for MAA, EAA, and BAA were determined to be from 2 to 4 ng/mL urine in 1 mL of sample size. This method is 5 to 10 times more sensitive than that using GC-FID. The method described here is superior to the existing ones reported in the literature in that it employs an easy sample treatment procedure and gives much higher recoveries, making it suitable for routine assays. The utility of this new method was demonstrated in a toxicology study of aliphatic alkyl ethers.

Exposure to glycol ethers in a population of French men evaluated by measurement of urinary alkoxycarboxylic acids.

Glycol ethers are solvents that are present in a large number of products used commercially and domestically. During recent years, ethylene glycol ether derivatives, in particular ethylene glycol methyl ether and ethylene glycol ethyl ether, have been progressively replaced by propylene glycol ether derivatives, which are less toxic. The aim of this study was to estimate the level of exposure to glycol ethers in a sample population of French men employed by the Paris Municipality by measuring the amount of alkoxycarboxylic acid metabolites in their urine. Urine samples were collected at the end of two different working weeks from 109 men, 54 of whom were judged to be occupationally exposed to glycol ether-containing products. Five alkoxyacetic acids (methoxyacetic, ethoxyacetic, n-propoxyacetic, phenoxyacetic, butoxyacetic acids) from ethylene glycol derivatives, and one alkoxypropionic acid (2-methoxypropionic) from a propylene glycol derivative, were simultaneously analysed by gas chromatography coupled to electron-capture detection. 2-Methoxypropionic was the most frequently found alkoxycarboxylic acid. The concentration of this metabolite reached 5.6 mmol/mol creatinine. The second most common alkoxycarboxylic acid was phenoxyacetic (up to 2.3 mmol/mol creatinine). The concentrations of the other alkoxycarboxylic acids were less than 1 mmol/mol creatinine. Although the concentration of alkoxycarboxylic acids was higher among men occupationally exposed to glycol ether-containing products than among unexposed men, the difference was significant only for butoxyacetic acid. Our data suggest that the use and exposure levels of glycol ethers have qualitatively and quantitatively changed dramatically over recent years. Particular attention should be paid in the future to alkoxypropionic acids derived from minor isomers of propylene glycol ether derivatives.

Hepatic enzymatic synthesis and hydrolysis of CoA esters of solvent-derived oxa acids.

Many ethylene glycol-derived solvents are oxidized to xenobiotic alkoxyacetic acids (3-oxa acids) by hepatic enzymes. The toxicity of these ubiquitous solvents has been associated with their oxa acid metabolites. For many xenobiotic carboxylic acids, the toxicity is associated with the CoA ester of the acid. In this study, related alkoxyacetic acids were evaluated as potential substrates for acyl-CoA synthetases found in mitochondrial, peroxisomal, and microsomal fractions isolated from rat liver. Likewise, chemically synthesized oxa acyl-CoAs were used as substrates for acyl-CoA hydrolases associated with the same rat liver fractions. Activities of the xenobiotic oxygen-substituted substrates were compared with analogous physiologic aliphatic substrates by UV-vis spectrophotometric methods. All of the solvent-derived oxa acids were reasonable substrates for the acyl-CoA synthetases, although their activity was usually less than the corresponding physiologic acid. Acyl-CoA hydrolase activities were decreased compared with acyl-CoA synthetase activities for all substrates, especially for the oxa acyl-CoAs. These studies suggest that these xenobiotic carboxylic acids may be converted to reactive acyl-CoA moieties which will persist in areas of the cell proximal to lipid synthesis, beta-oxidation, protein acylation, and amino acid conjugation. The interaction of these xenobiotic acyl-CoAs with those processes may be important to their toxicity and/or detoxification.

Rat model for renal effects of 2-alkoxyalcohols and their acetates.

Male Wistar rats were given ethanediol (9.4 g/l), 2-ethoxyethylacetate (5.4 g/l), 2-butoxyethylacetate (2.9 g/l) and 1,2-propanediol (40 g/l) respectively in their drinking water for 2 weeks. Urine was collected during the last 24 h of the exposure. There was a marked increase in the oxalic acid excretion by the rats given ethanediol while rats given the alkoxyacetates excreted large amounts of ethoxyacetic and butoxyacetic acid, respectively. While not increased compared with controls, the excretion of oxalic acid by the latter group of rats was correlated to the excretion of the respective alkoxyacetic acids. The ammonia and glycosaminoglycan excretion was also smaller than that of controls. The urinary activity of succinate dehydrogenase was decreased in rats given the alkoxyacetates but not in animals exposed to ethanediol or propanediol. The data show that oxalic acid is actually a minor metabolite of the alkoxyacetates while the biochemical effects in kidney are associated more with the alkoxyacetic acid load. Alkoxyacetic acids seem to be inhibitors of renal succinate dehydrogenase, which may account for the decreased ammonia and glycosaminoglycan excretion.

Improved method to measure urinary alkoxyacetic acids.

OBJECTIVES: To simplify the current preparation of samples, and to improve the specificity and reliability of the conventional analytical methods to measure urinary alkoxyacetic acids. METHODS: Samples containing alkoxyacetic acids...

Theoretical Study of the Mechanisms for the Alkoxyacetic Acids Decomposition

The decomposition of three alkoxyacetic acids, methoxy, ethoxy, and isopropoxy acetic acids, has been studied by using ab initio calculations at the MP2/6-31G** level. Molecular mechanisms A and B have been characterized, corresponding to stepwise processes with formation of the corresponding alcohol and an α-lactone intermediate, achieved by the nucleophilic attack of either carbonylic or hydroxylic oxygen atoms followed by a ring opening process to yield formaldehyde and carbon monoxide. For ethoxyacetic and isopropoxyacetic acids, three additional reactive channels were thought to be possible on potential energy surface; mechanisms C and D are elimination processes to give the corresponding alkene and glycolic acid. The reaction pathways along mechanisms C and D take place by the transfer of a β-hydrogen atom, with respect to the ether group, from the terminal methyl group to the hydroxylic or the alkoxylic oxygen atoms, respectively. The glycolic acid formed in the first step is then submitted to decomposition by water elimination and α-lactone intermediate formation. A final ring opening process yields formaldehyde and carbon monoxide. Molecular mechanism E is associated with a fragmentation process along a concerted one-step with concomitant formation of the corresponding alquene, formaldehyde, water, and carbon monoxide. The decomposition process is energetically favorable along the mechanism A, and the calculated rate coefficients agree with experimental data.

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.

Correspondence between occupational exposure limit and biological action level values for alkoxyethanols and their acetates.

The Finnish occupational exposure limit (OEL) values for alkoxyethanols and their acetates were lowered in 1996. A reevaluation of the correspondence between the new OEL value and the biological action level (BAL) was thus needed. This study was conducted in silkscreen printing enterprises, where 2-alkoxyethanols and their acetates are mainly used as solvents. The air/urine correlations between 2-methoxyethylacetate, 2-ethoxyethylacetate, 2-butoxyethanol, 2-butoxyethylacetate, and 2-methoxyacetic (MAA), 2-ethoxyacetic (EAA), and 2-butoxyacetic acid (BAA) were evaluated on an individual and time-related basis at four different enterprises. Inhalation exposure to alkoxyalcohols and their acetates was monitored with diffusion badges (n = 38) for an entire work week. Urinary excretion of alkoxyacetic acids immediatley after the shift and at 14-16 h after exposure (n = 112) was analyzed by a gas chromatograph equipped with a flame-ionization detector. Inhalation exposure to 2-methoxyethylacetate at 0.5 cm3/m3 corresponded to MAA excretion of 3 mmol/mol creatinine in urine at 14 to 16 hours after exposure. The next-morning urinary EAA excretion of 37 mmol/mol creatinine corresponded to an 8-h 2-ethoxyethylacetate exposure of 2 cm3/m3 when all collected data were included. This average EAA excretion was 69% of the German BAT value and only 34% of the American biological exposure index (BEI) value. Urinary EAA excretion was 30-40% lower at the beginning of the work week than at the end of the work week. On the other hand, EAA excretion was 10-20% higher than that measured at 14-16 h after exposure. Urinary BAA excretion of 75 mmol/mol creatinine in postshift urine corresponded to an 8-h 2-butoxyethanol and 2-butoxyethylacetate exposure of 5 cm3/m3. This BAA excretion was 87% of the German BAT value. According to these results, it seems that the BAL for MAA and EAA should be 3 and 50 mmol/mol creatinine as measured at 14-16 h after exposure, respectively. The BAL value for BAA seems to be 70 mmol/mol creatinine in postshift samples. These recommendations are valid only if samples are collected at the end of the work week.

Urinary alkoxyacetic acids and renal effects of exposure to ethylene glycol ethers.

Ethylene glycol ethers and their acetates are widely used in industry, because of their hydrophilic and simultaneously lipophilic properties. Ethylene glycol ethers and their acetates are mainly metabolised to alkoxyacetic acids, but there is also a minor pathway through ethylene glycol to oxalic acid. The main pathway of ethylene glycol ethers is associated with significant clinical or experimental health effects and the minor pathway is also interesting because formation of urinary stones depends principally upon the urinary concentration of oxalate and calcium. Excretion of alkoxyacetic and oxalic acids was examined among silkscreen printers for an entire working week. The aim of the study was to evaluate alkoxyacetic acids as early indicators of exposure to glycol ethers and to evaluate their toxicity to kidneys. The load of alkoxyacetic and oxalic acids was compared with the excretion of calcium, chloride, ammonia, and glycosaminoglycans (GAG). Morning urine was chosen for the main analysis, as the overall metabolite, ethoxyacetic acid (EAA), has a long elimination time from the body. The excretion of calcium increased according to the urinary alkoxyacetic acid load. The excretion of ammonia and chloride was higher among the exposed workers than among the controls. The highest urinary alkoxyacetic acid load was also associated with increased excretion of GAG, which may reflect the toxicity of metabolites of ethylene glycol ether. The excretion of GAG correlated positively with that of calcium in the printers with highest exposure. The tendency to form urinary stones was 2.4-fold higher among silkscreen printers than among office workers. On the basis of renal effects our study indicates the need for establishing a new biological exposure limit before a workshift that is clearly below 100 mmol ethoxyacetic acids per mol creatinine in morning urine of people occupationally exposed to ethylene glycol ethers.

Determination of urinary alkoxyacetic acids by a rapid and simple method for biological monitoring of workers exposed to glycol ethers and their acetates.

In control subjects and workers exposed to glycol ethers and their acetates, we determined the urinary metabolites (three alkoxyacetic acids) by a simple and rapid method. Levels of urinary metabolites were significantly higher in the solvent workers than in the nonexposed subjects. The exposure levels measured by personal monitoring of breathing zone air were far below the threshold limit value. The present results indicate that determination of urinary alkoxyacetic acids by the practical method used here is useful for evaluating excessive exposure to solvents.

Analysis of ethylene glycol ether metabolites in urine by extractive alkylation and electron-capture gas chromatography.

Alkoxyacetic acids are metabolically formed and excreted in urine after exposure to ethylene glycol monoalkyl ethers (alkoxyethanols) or their acetate esters. This paper presents a sensitive method based on extractive alkylation for determination of alkoxyacetic acids in urine. Alkoxyacetate ions were extracted from 200 microliters urine into methylene chloride, with tetrabutylammonium acting as counter ion, and derivatized with pentafluorobenzyl bromide in a single step. After separation of the methylene chloride phase, evaporation, and dissolution of the residues in hexane the esters were analyzed by fused silica capillary column gas chromatography and electron capture detection. The esters formed were stable for at least 2 weeks at room temperature. The limit of quantification was estimated to 2 microM (corresponding to an injected amount of 2 pg) for methoxyacetic (MAA) and ethoxyacetic acid (EAA) in urine. The corresponding values for butoxyacetic acid (BAA) were 4 microM and 5 pg, respectively. The detector response was linear up to 80 microM and the formation of derivative at least up to 1 mM. The method error may be reduced by using a second alkoxyacetic acid derivative, EAA, BAA or 2-pentoxyacetic acid (PAA), as an internal standard. The sensitivity, stability, reduced number of extractions, and small volumes of reagents and sample needed make the present method useful in biomonitoring of occupational exposure to ethylene glycol ethers.

Structure-activity relationships for the in vitro hematotoxicity of N-alkoxyacetic acids, the toxic metabolites of glycol ethers

Ethylene glycol mono- n-alkyl ethers are a major class of industrial chemicals which cause a wide range of toxic effects in laboratory animals including reproductive and developmental toxicity, as well as hematotoxicity. Alkoxyacetic acids are the major metabolites of ethylene glycol ethers and are considered to be the proximate toxic metabolites. The structure-toxicity relationships of these acids are well documented in the reproductive and developmental systems. Therefore, current studies were conducted to investigate the structure-activity relationships of these acids for hematotoxicity in rat blood in vitro. Results presented here indicate that the effects of various alkoxyacetic acids on rat erythrocytes are qualitatively similar and comprise early swelling followed by hemolysis. The ranking of the activity of these acids was as follows: butoxyacetic acid (BAA)>propoxyacetic acid ≅ pentoxyacetic acid > ethoxyacetic acid>methoxyacetic acid. Furthermore, this effect of alkoxyacetic acids was associated with a parallel decrease in blood ATP levels. It is currently unknown if swelling or ATP depletion is the primary effect of these acids. In addition, at equimolar concentrations neither heptanoic, butoxypropionic, nor propoxypropionic acids caused any significant effect on rat erythrocytes in vitro. This suggests that the presence and position of the ether linkage, as it is in BAA, are critical for the development of hematotoxicity. Studies of the relationship between the toxic effect of BAA and its partitioning between erythrocytes and plasma showed that the concentration of [ 14C]BAA in plasma remained relatively constant while that in the erythrocytes increased as a function of time. This pattern of BAA distribution between plasma and erythrocytes was parallel to erythrocyte swelling. Incubation of BAA with rat blood for 30 min followed by removal of BAA by washing the erythrocytes twice and then continuing the incubation revealed that erythrocyte swelling was not reversible, however, the rate of swelling declined significantly.

Biological monitoring of exposure to ethylene glycol ethers.

Glycol ethers are frequently used in industry for painting, printing, and cleaning purposes. The methyl and ethyl ethers of ethylene glycol (EGME and EGEE), as well as their acetate esters EGMAc and EGEAc, are teratogenic and embryotoxic and cause testicular damage in laboratory animals. The adverse effects have been attributed to the metabolites methoxyacetic (MAA) and ethoxyacetic acid (EAA). Alkoxyacetic acids appear to be suitable biological indices of exposure as these acids are not normally present in human urine. The influence of workload and of skin uptake on the internal dose are accounted for by urine monitoring. In addition, the concentration or excretion rate of acid metabolite in urine may correlate with target organ dose of active agent, and thus with the health hazard better than the ambient air level of glycol ether (Johanson 1988).

Comparison of the in vivo and in vitro testicular effects produced by methoxy-, ethoxy- and N-butoxy acetic acids in the rat

Methoxy-, ethoxy- and n-butoxy acetic acids, known urinary metabolites of the corresponding alkoxyethanol solvents, were administered by gavage to rats as a single oral dose equimolar with 500, 250 or 100 mg 2-methoxy-ethanol/kg body weight. Testicular weight and morphology were monitored over a 14-day period post-treatment. Methoxyacetic acid (MAA) was the only compound which produced a significant decrease in testicular weight. Histological examination of the testes from treated animals indicated that MAA at all doses and ethoxyacetic acid (EAA) at the highest dose, produced damage specific to spermatocytes undergoing meiotic maturation and division (particularly stages XIII–XIV) within 24 h of treatment. n-Butoxyacetic acid (BAA) had no discernable effect on the testis at any dose level or time, although there was evidence of haematuria produced by the compound. Addition of MAA, EAA and BAA to testicular cell cultures at concentrations approximately equivalent to the steady state plasma levels of MAA determined after a testicular toxic dose (500 mg/kg) of methoxyethanol (5 mM) produced a specific loss of pachytene spermatocytes (the target BAA did not produce any specific changes to testicular cell populations in vitro. Thus the production of testicular toxicity by alkoxyacetic acids diminishes with increasing chain length, and a good correlation exists between in vivo and the in vitro system.