K. J. Freundt

Ethanol - Induced Accumulation of Ethylene Glycol Monoalkyl Ethers in Rats

In adult female SPF Sprague-Dawley rats, exposed for 2 hours to 2-methoxy-ethanol (ME, 1600 ppm), 1-acetoxy-2-methoxy-ethane (AME, 800 ppm), 2-ethoxy-ethanol (EE, 420 ppm), or 1-acetoxy-2-ethoxy-ethane (AEE, 170 ppm) the blood level of ME (after ME or AME) or EE (after EE or AEE) was considerably increased after pretreatment with ethanol (20 mmol/kg b.w. i.p.). (ME and EE are metabolites of AME and AEE, respectively.) After i.p. co-administration of ME (10 mmol/kg), EE (10 mmol/kg) or butoxy-ethanol (BE, 2.5 mmol/kg) with ethanol (20 mmol/kg) the blood level of ME, EE, and BE remained nearly constant as long as ethanol levels in blood were above 3 mmol/l. Repeated i.p. dosing (5 times one injection per hour) with EE (4 mmol/kg) or ME (5 mmol/kg) plus ethanol (8 or 10 mmol/kg) each resulted in an almost complete accumulation of both ether compounds in the blood. Blood levels of ethanol were increased significantly after EE, but only slightly after ME administration. The prolonged retention of ME, EE, or BE is due to an inhibition of the degradation of these compounds following the competition with ethanol at the alcohol dehydrogenase, the common metabolizing enzyme. This study has demonstrated that glycol ether derivatives are extremely accumulated as long as only very low levels of ethanol are present in blood. Therefore, it is concluded that the elimination of the investigated glycol ethers after occupational exposure can be retarded in alcoholized employees causing an increased health risk of these chemicals following the consumption of alcoholic beverages.

Toxicity studies in fertilized zebrafish eggs treated with N-methylamine, N,N-dimethylamine, 2-aminoethanol, isopropylamine, aniline, N-methylaniline, N,N-dimethylaniline, quinone, chloroacetaldehyde, or cyclohexanol

N-methylamine~ N~N-dimethylamine, 2-aminoethanol, isopropylamine, aniline, N-methylaniline, N,N-dimethylaniline, quinone~ chloroacetaldehyde, cyclohexanol are widely used in various industrial fields (Merck Index 1989). They may therefore contaminate the environment. Their possible embryotoxic and/or teratologic potency has not been published before (GRS 1992)~ except that of aniline (Price et al. 1985, Hardin et al. 1987). This gap could be filled by the investigation presented here. Ferti l ized zebrafish (Brachydanio fetiD) eggs served as a well-recognized test object (Baumann and Sander 2984; Van Leeuwen et al. 1990) to elucidate morphological changes in the fish embryo during development and to discover reduction of the hatching rate induced by the above mentioned xenobiotics. From the results information important for the assessment of health risk are to be expected.

Rise of inhaled toluene, ethyl benzene, m-xylene, or mesitylene in rat blood after treatment with ethanol

Toluene, ethyl benzene, m-xylene, and mesitylene (1,3,5-methyl benzene) are widespread as solvents in industries and laboratories or in the manufacture and application of glues, paints, printing inks etc. These aromatics may be absorbed by employees during exposure at the workplace. Alcoholic beverages may be consumed during occupational inhalation or after shifts end at times. Toxicokinetic interactions between the aromatics and ethanol must be assumed because of the common pathway of biotransformation. The blood levels of toluene and m-xylene after inhalation increased significantly in volunteers dosed simultaneously with ethanol. In this view the present experiments in rats should elucidate whether the blood concentrations of inhaled ethyl benzene and mesitylene (both structurally related to toluene and m-xylene) can rise under the influence of ethanol, and whether quantitative differences of this effect due to the structure of these aromatics can occur. From the results informations important for the assessment of occupational health risk are to be expected.

Blood Acetaldehyde Levels in Alcohol-Dosed Rats After Treatment with Anit, Antu, Dithiocarbamate Derivatives, or Cyanamide

In adult female Wistar rats, pretreated by gavage with two doses - 16 or 256 mumol/kg - of cyanamide, TMTD (tetramethylthiuram disulfide), TMTM (tetramethylthiuram monosulfide), Ziram or Zineb at 90 min or 18 h before administration of 2 g of ethanol/kg i.p., the blood acetaldehyde levels were significantly increased for 90 - 240 min after ethanol administration (exceptions were noted after exposure to Zineb for 90 min or to low-dosed cyanamide for 18 h). After pretreatment for identical periods with ANTU (N-1-naphthylthiourea) or ANIT (1-naphthylisothiocyanate) at doses extending into the LD50 range, the blood acetaldehyde levels of rats given the same dose of ethanol remained uninfluenced. The increase in blood acetaldehyde recorded after 16 mumol/kg p.o. of TMTM and TMTD remained detectable for up to 48 h. Onset of the cyanamide action occurred already after 45 min. While recognizing that results from animal experiments cannot be transposed without restriction to the human situation, it is concluded that occupational contacts with ANTU or ANIT are not likely to elicit increased blood acetaldehyde levels in man after ingestion of alcohol. The risk of an ethanol intolerance reaction due to a rise in blood acetaldehyde therefore does not appear to be warranted. The present findings indicate, however, that exposure to TMTD, TMTM, Ziram, Zineb or cyanamide is associated with a definite health risk; because of the long persistence of these substances in the body, the risk exists for a long time post-exposure.

Influence of Pb, Cd, Zn, Mn, Cu, Hg, or Be salts on the glutathione S-transferases of the rat liver

Earlier investigations revealed different interactions of metal-free and metal-containing thiurams (Fungicides, rubber accelerators) with GST or rat livers. Based on these observations the question arose whether heavy metals alone may influence the activity of GST. In vitro experiments with isolated GFST showed different interactions. The activity of the GSH S-acyltransferases in liver, kidney, lung and brain of mice were enhanced by treatment with CdCl{sub 2}, HgCl{sub 2} or NaCO{sub 3}; in contrast the activity of GSH S-epoxide transferase in the liver of mice was decreased by Cd, Hg or V containing salts. The objective of the authors study was to explore the effects of Pb, Cd, Zn, Mn, Cu, Hg and Be ions on the glutathione-conjugating enzyme system (GSH S-epoxide transferase, GSH S-aryltransferase) during long-term administration (3 months) as compared to in vitro exposure.

Pharmacokinetics of inhaled carbon disulphide in rats in relation to its inhibitory effect on the side-chain oxidation of hexobarbital.

SummaryIn acute inhalational exposure even low doses of carbon disulphide (CS2) inhibit the oxidative drug metabolism: This inhibition, studied by the example from the side-chain oxidation of hexobarbital, increases steadily in adult female rats during exposure to 100 ppm over 8 hrs, as shown by the prolonged hypnotic-narcotic effect; it is completely reversible within 24 hrs so that repeated identical doses of CS2 do not give rise to a cumulative effect. The cause of this phenomenon is an inhibition of the microsomal oxydative enzyme system in the liver, as could be demonstrated in purified enzyme preparations from liver homogenates of rats exposed to 50 ppm CS2 over 2–8 hrs. This inhibitory effect is intimately linked with the presence of CS2 in the organism, as seen from its pharmacokinetic behaviour. In the course of an 8-hr inhalation (400 ppm CS2) the rate of saturation in the blood and liver is most rapid during the first few hours. After the termination of the exposure CS2 is distributed in the blood and liver at a ratio of 3:2. Approximately one third of the CS2 that has passed into the liver is found in the isolated microsomas where it is detectable for several hours. Elimination of the inhaled CS2 from the blood and liver occurs at a halflife of 35 min and 65 min, respectively. The preferred route of elimination is by exhalation, approximately 10% of the14CS2 activity being recovered within 4 hrs following subcutaneous injection of14CS2. Significant oxidation of CS2 to urinary sulphate has not been found to occur after inhalation. Since the inhibition of the microsomal mixed-function oxygenases due to inhaled CS2 occurs primarily during its retention in the organism, it is concluded that initially CS2 itself acts as the inhibitor, but it appears probable that CS2 metabolites (for example, thiurams) are also implicated.

Ferrous sulfate combined with ascorbic acid does not significantly reduce acetaldehyde accumulation in the blood of alcoholized rats treated with disulfiram or betalactam antibiotics

Adult female SPF Sprague-Dawley rats treated orally by gavage with disulfiram (1 g/kg b.wt.) or betalactam antibiotics (3.38 mmol/kg b.wt.) with a 1-methyltetrazole-5-thiol side chain (cefmenoxime, latamoxef, cefotetan, cefoperazone, cefamandole) produced a marked, statistically significant rise of acetaldehyde in the blood 1 and 3 hr following IP administration of ethanol [2 g/kg b.wt., 20% (g/v) solution]. This accumulation of blood acetaldehyde remained unchanged or was reduced only very slightly by a mixture of iron sulfate [Fe(II)SO4.7H2O, 2.64 mg/kg b.wt.] and ascorbic acid (6.67 mg/kg b.wt.) injected intravenously. This slight decrease is considered to be due to a formation of a complex between ferrous sulfate and agents (disulfiram and the betalactam antibiotics as well as their metabolites) producing acetaldehyde by inhibition of acetaldehyde metabolizing enzymes. A possible coaction of ascorbic acid cannot be explained satisfactorily; ascorbic acid may support cellular redox potentials. The combination of ferrous sulfate and ascorbic acid was used for examination since both chemicals are recommended to reduce adverse symptoms of an ethanol incompatibility reaction in the course of a therapy with the mentioned antibiotics or disulfiram. Since acetaldehyde augmentation in the blood is regarded as a cause of complaints and because the acetaldehyde rise was not depressed significantly by ferrous sulfate and ascorbic acid it can be concluded that these two agents are not potent enough for a rational therapy of ethanol incompatibility symptoms initiated by the investigated drugs.

Delayed Ethanol Elimination in Rats after Application of Cefamandole or Cefoperazone

Adult female Sprague-Dawley rats received ethanol (2 g/kg b.w., i.p.) 18 hours after pretreatment with the betalactam-antibiotics cefamandole (CMD) or cefoperazone (CPZ) (1 mmol/kg b.w. each, i.p.). The blood ethanol concentrations, determined repeatedly within 4 hours by head space GC, were increasingly elevated after CMD or CPZ up to twice the respective control values. The possible clinical and forensic significance of these findings for the therapeutic use of CMD or CPZ is pointed out.

Toxicity studies on tetramethylthiuram monosulfide

Abstract Tetramethylthiuram monosulfide (TMTM), when given in a small dose of 26 mg/kg po, caused prolongation of the hexobarbital sleeping time in female Wistar rats. This effect was enhanced by increasing the dose to 867 mg/kg po and was associated with a lengthening of the zoxazolamine paralysis time. Both effects are causally related to an inhibition of the microsomal monooxygenases. One of the reasons for this inhibition conceivably is the concomitant decrease in the conversion of palmitic acid (incorporation of 14 C radioactivity) into the phospholipids of the microsomal membrane. In contrast, other clinicochemical parameters of liver function detectable in the blood remained normal even after oral doses of 26 mg/kg TMTM administered on 5 consecutive days per week over a period of 4 weeks. However, this treatment caused a decrease in the erythrocyte count and hemoglobin content in the blood, together with a reduction of the relative liver weight, body weight, and the intake of food, while the consumption of drinking water was increased. Histologically, there was evidence of hepatocellular and renal tubular swelling. In female mice given acute oral doses of TMTM, the LD 50 was calculated as 818 (583–995) mg/kg. In mutagenicity tests, TMTM caused point mutations in strains TA 100 and TA 1535 ( Salmonella typhimurium LT 2). The results indicate that the toxic potential of TMTM is comparable to that of other thiurams. A tentative hygienic threshold limit of 5 mg/m 3 is proposed for the working environment.

Diminution of ethanol-induced hyperglycaemia in the rat by administration of beta-lactam antibiotics with a tetrazole thiol group

The acute-onset hyperglycaemia produced by i.p. injection of 2 g of ethanol/kg body weight in adult female SPF Sprague-Dawley rats (200-220 g) was considerably less pronounced when 100 mumol/kg b.w. of one of the following tetrazole thiol-containing beta-lactam antibiotics (BLAs) was given i.p. 3 hours in advance: cephamandole (CMD), moxalactam (MOX), cephoperazone (CPZ) or cephothiam (CTM). An equimolar dose of cephazolin (CEZ), a thiadiazole thiol-containing cephalosporin, did not affect the ethanol-induced hyperglycaemia. Administration of an equimolar oral dose of disulfiram, which has an NCS structure similar to that of the tetrazole thiol-containing BLAs, produced an additional increase of the ethanol-induced hyperglycaemia. The diminution of the ethanol-induced hyperglycaemia by BLAs with a tetrazole thiol group appears to be linked to their NCS structure. It is conceivable that this effect which might be important for human therapy, is causally related to an inhibition of the glycolytic or gluconeogenetic enzyme system.