P.Th. Henderson

Determination of hydroxylated metabolites of polycyclic aromatic hydrocarbons in urine

9,101, show excess rates of lung cancers. Estimates of the health risks due to environmental or occupational exposure to these compounds strongly depend on the quality of analytical methods used to assess the intake or uptake of PAHs. In this respect, an important role is played by biological monitoring, i.e. the systematic registration of the exposure level of individual workers and groups of workers, measured in biological specimens. PAHs are metabolized extensively and the enzymes involved are classified in two broad categories: phase 1 enzymes, which catalyse oxidative reactions, and phase 2 enzymes, which catalyse conju- gative reactions of oxidized PAHs with endogenous compounds such as sulphuric acid, glucuronic acid and glutathione. PAH metabolites may be excreted either as free or as conjugated compounds. The known carcinogenic PAHs are of a large molecular type

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.

Mutagenicity of urine from nurses handling cytostatic drugs, influence of smoking

SummaryMutagenicity towards Salmonella typhimurium TA 100 of urine from smoking nurses, who were occupationally involved in the treatment of patients with cytostatic drugs, was significantly increased in comparison with that of smoking control subjects. Mutagenicity towards Salmonella typhimurium TA 100 was not increased in exposed non-smokers when compared to control non-smokers. In smoking subjects urinary mutagenicity appeared increased towards Salmonella typhimurium TA 1538 in the presence of S-9 mix.Rats pretreated with Aroclor 1254 showed higher mutagenicity in their urine than untreated rats after cyclophosphamide administration. Therefore, the synergistic effect of smoking might be due in part to induction of enzymes involved in the mutagenic activation of cytostatic drugs. Further, the animal experiments showed that cyclophosphamide (the most frequently used mutagenic cytostatic drug) can be absorbed after oral or percutaneous administration. Therefore, it is not excluded that differences in working hygiene between smokers and non-smokers also play a role.

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.

Urinary mercapturic acid excretion as a biological parameter of exposure to alkylating agents.

SummaryMercapturic acid derivatives or other thioethers can be considered as the endproducts of the metabolic detoxification of possibly alkylating agents. It is proposed that the appearance of these metabolites in the urine can be used as an indicator of exposure of the organism to such toxic compounds. A simple, practical procedure for determination of thioethers in urine samples is described. Employees of chemical and metal industries have been compared with respect to their urinary thioether concentrations. It was found that chemical workers excreted more thioether compounds than persons engaged in metal industry.

Metabolites of the plasticizer di(2-ethylhexyl)phthalate in urine samples of workers in polyvinylchloride processing industries

SummaryLittle is known about occupational exposure to the plasticizer di(2-ethylhexyl)phthalate (CAS number 117-81-7), a compound widely used in polyvinylchloride (PVC) plastics. We have studied the uptake of DEHP in workers by determining the concentrations of four metabolites of DEHP in urine samples, i.e., mono(2-ethylhexyl)phthalate (MEHP), mono (5-carboxy-2-ethylpentyl)phthalate, mono(2-ethyl-5-oxohexyl)phthalate, and mono(2-ethyl-5-hydroxyhexyl)phthalate. In addition DEHP concentrations in the air were determined by personal air sampling. Nine workers in a PVC boot factory exposed to a maximum of 1.2 mg/m3 DEHP showed an increase in the urinary concentrations of all four metabolites over the workshift. These results were obtained on both the first and the last day of the workweek. With the exception of MEHP, the increases in the concentrations of the metabolites during a workday were statistically significant. Six workers from a PVC cable factory exposed to a maximum of 1.2 mg/m3 DEHP showed a one-to fourfold increase in the concentrations of the four metabolites over the workshift, but these increases were not statistically significant. These results indicate that measurement of DEHP metabolites in urine samples may be of use for monitoring the occupational exposure to DEHP.

Metabolism of drugs during rat liver regeneration

Abstract Enzymatic activities for the p-hydroxylation of aniline, the N-demethylation of aminopyrine, and the UDPglucuronyl conjugation of p-nitrophenol of regenerating rat liver have been measured in vitro at different intervals following partial hepatectomy. The p-hydroxylating and N-demethylating activities decreased during the period of rapid cellular proliferation and subsequently rose to about 100 and 80 per cent respectively of their initial values within 7 days postoperatively. The UDPglucuronyltransferase activity, measured in ultrasonicated homogenates, however was not reduced during the regeneration process. Pretreatment of the rats with phenobarbital resulted in a considerable increase of the drug-oxidizing enzymes even during the period of rapid growth. The possibility that the changes of drug-oxidizing capacities of regenerating liver are related to the rate of liver growth is considered.