Ch.-M. Leijdekkers

1-Hydroxypyrene in human urine after exposure to coal tar and a coal tar derived product

SummaryA method for isolating 1-hydroxypyrene from urine is described. The presence of 1-hydroxypyrene in urine was identified by fluorescence excitation and emission scanning after HPLC-separation. 1-Hydroxypyrene could be detected in the urine of rats following oral administration of as little as 0.5 μg pyrene. The dose-dependence of 1-hydroxypyrene in urine was evident after a wide range of pyrene dosing. After therapeutical coal tar treatment of dermatological patients the enhanced excretion of 1-hydroxypyrene was highly significant. Employees of a creosote impregnating plant showed an excretion pattern of 1-hydroxypyrene which could be related to their work. 1-Hydroxypyrene in urine of non-exposed people was very low, but detectable. It is suggested that the method reported is suitable for the assessment of uptake of man to pyrene, a compound that is commonly present in work environments which are associated with pollution of polycyclic aromatic hydrocarbons.

Synergistic effects of phorone on the hepatotoxicity of bromobenzene and paracetamol in mice

Administration of phorone (diisopropylidene acetone), an industrial solvent, to mice caused a rapid depletion of hepatic glutathione, which is due to enzymatic conjugation of phorone with glutathione, mediated by cytoplasmic enzymes of the liver. Whereas phorone, even in high doses, did not show hepatotoxic effects by itself, combined administration of phorone with a subtoxic dose of either paracetamol or bromobenzene strongly enhanced hepatotoxicity of the latter compounds as was judged from a rise in serum transaminase activities. These findings are compatible with the concept of a dose threshold for biologically reactive intermediate compounds which are bioinactivated through glutathione conjugation.

Thioether concentration and mutagenicity of urine from cigarette smokers

SummaryUrinary thioether compounds, such as mercapturic acids, can be considered as nontoxic end products of potentially alkylating agents. On the other hand, urinary mutagenicity may represent the excretion of potential mutagens that have not definitively been detoxified by the organism. It is suggested that a combined urinary thioether and mutagenicity test may be useful in monitoring people occupationally exposed to potentially alkylating compounds, in particular to mixtures of these chemicals. Exposure to cigarette smoke, containing several known mutagens and carcinogens, is expected to interfere with the test results.The excretion of mutagens and thioethers was determined in urine of smokers and nonsmokers. Smokers excrete more mutagens and thioether compounds than nonsmokers. Further, it was found that the urinary mutagenicity and thioether level are significantly related to the amount of cigarettes smoked.

Detection and identification of S-methylcysteine in urine of workers exposed to methyl chloride

SummaryMethyl chloride is used as a methylating agent and as a blowing agent in industrial processes. Alkylating agents and other electrophilic compounds are often detoxified in the organism through conjugation with glutathione. Glutathione conjugates are generally excreted as mercapturic acids, cysteine conjugates, or other thioethers in urine.Urine samples obtained from persons occupationally exposed to methyl chloride were examined for the presence of elevated thioether levels using a previously published non-selective procedure. No significant increases were detectable.A new assay procedure was developed for the detection of methylthio compounds in urine. The method is based on alkaline hydrolysis of urine samples and subsequent gas chromatographic determination of methyl mercaptan in the headspace of acidified hydrolysates. By application of this method a greatly increased excretion of a methylthio compound in the urine of CH3Cl-exposed workers was shown. The compound was identified as S-methylcysteine.A study of the urinary S-methylcysteine excretion in a group of workers during a seven-day shift revealed that two of six workers hardly excreted any S-methylcysteine after exposure to methyl chloride.

Effect of toluene and xylenes on liver glutathione and their urinary excretion as mercapturic acids in the rat

Administration of toluene and xylenes to rats caused a decrease in liver glutathione concentration. The effect was most pronounced after the administration of o-xylene. 26% of the initial glutathione level was found three hours after treatment with o-xylene (4.0 mmoles/kg).No in vitro conjugation of o-xylene with glutathione was observed, neither spontaneously nor in the presence of 105,000 g supernatant from rat liver homogenate, containing glutathione S-transferases. Thus, a metabolite of o-xylene, which is not formed during incubation with 105,000 g supernatant, reacts with glutathione.A thioether was isolated from urine of rats given o-xylene; the compound was identified as o-methylbenzyl mercapturic acid by GC-MS and NMR. Chromatographic evidence was found for the presence of benzyl mercapturic acid in the urine of toluene-treated rats. The amounts of mercapturic acids excreted in the urine after administration of toluene, p-xylene, m-xylene, and o-xylene were 0.4–0.7, 0.6, 1.3, and 10–21% of the dose, respectively.These results demonstrate the involvement of a thusfar unknown pathway in the biotransformation of toluene and xylenes.

Identification and determination of 2-thiothiazolidine-4-carboxylic acid in urine of workers exposed to carbon disulfide

A compound was isolated from the urine of workers exposed to carbon disulfide during the production of rayon. The compound was identified as 2-thiothiazolidine-4-carboxylic acid (TTCA) by GC/MS and NMR. A HPLC method for the quantitative determination of TTCA was elaborated and applied to urine samples. The method allowed detection of TTCA concentrations in urine as low as 5 × 10−7 M.No TTCA was detected in urine of workers occupationally exposed to organic solvents other than CS2. High concentrations of TTCA (upto 32×10−5 M) were shown to be present in urine of spinners exposed to CS2 concentrations of approximately 100 mg/m3. It is suggested that the assay of urinary TTCA is suitable for detection of occupational exposure to CS2.

Enhanced excretion of thioethers in urine of operators of chemical waste incinerators.

Thioether concentrations were determined in urine samples obtained from ten workers in the despatch department (n = 69), three chemical waste incinerator operators (n = 67), and an analyst (n = 21), all working in the same chemical plant. Urine samples (n = 196) obtained from non-exposed men, including smokers, served as controls. Enhanced excretion of thioethers was found in urine samples taken from incinerator workers at the end of work. A regular pattern in the time course of the urinary thioether excretion was shown by a non-smoking incinerator worker; end-of-work values were always higher than prework values. This phenomenon was not found in samples obtained from the analyst. These findings suggest that incinerator workers inhale or otherwise absorb electrophilic compounds or their precursors, which are subsequently metabolised to, and excreted as, thioethers in urine.

Determination of Thio Compounds in Urine of Workers Exposed to Carbon Disulfide

Metabolites of carbon disulfide excreted into the urine of viscose workers are detectable by application of a nonselective assay for the determination of thio compounds. Enhanced secretion of thio compounds occurred especially at the end of the workday in exposed workers. A classification of urine samples according to the degree of exposure gave evidence for a relation between exposure to carbon disulfide and excretion of thio compounds in urine. The presence of 2-thiothiazolidine-4-carboxylic acid in urine of viscose workers was indicated by TLC, UV-spectrometry, and HPLC.

The presence of the mutagenic polycyclic aromatic hydrocarbons benzo[a]pyrene and benz[a]anthracene in creosote P1

Several fractions of creosote P1 separated by TLC showed mutagenicity towards Salmonella typhimurium TA98. Thus mutagenicity is probably caused by the presence of mutagenic aromatic hydrocarbons. The mutagenic polycyclic aromatic hydrocarbons, benzo[a]pyrene and benz[a]anthracene, were detected in concentrations of 0.18 and 1.1% respectively. Because these compounds are probably not essential for the wood-preserving properties of creosote , a more selective composition of the product should be considered.

Metabolism of benzidine-based dyes and the appearance of mutagenic metabolites in urine of rats after oral or intraperitoneal administration.

The azo reduction and acetylation in vitro and the mutagenic activation in vivo of three azo dyes were studied. In the presence of rat-liver 9000 g supernatant benzidine was released from direct black 38 and direct brown 95, whereas hardly any benzidine was produced during incubation of direct blue 6. Incubation of benzidine with isolated rat hepatocytes resulted in the appearance of diacetylbenzidine. No diacetylbenzidine was formed during incubation of benzidine with rat-liver 9000 g supernatant, unless the cofactor for the acetylation reaction, acetyl coenzyme A, was added to the incubation medium. Isolated rat hepatocytes were capable to produce diacetylbenzidine from direct black 38, direct blue 6 or direct brown 95 without supplementation with acetyl coenzyme A. Administration of benzidine, direct black 38 or direct brown 95 to rats resulted in the appearance of mutagenicity in urine. For direct black 38 significantly higher mutagenicity values were found in urine after oral administration than after intraperitoneal treatment. Such differences were not observed for benzidine and direct brown 95. The results demonstrate that rat liver has a considerable capacity to reduce azo compounds. Nevertheless, for some compounds, like direct black 38, extrahepatic enzymes, most likely present in the intestinal flora, may also play a substantial role in the azo cleavage.