J.L.G. Theuws

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.

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.

Excretion of mutagens in human urine after passive smoking.

Eight non-smokers were experimentally exposed to cigarette smoke by staying in a poorly ventilated room together with heavy smokers for 6 h. Air samples were taken and the extract appeared to contain mutagenic substances. This is in accordance with the presence of carcinogens in tobacco smoke. Inhalation of the contaminated air by the passive-smokers resulted in an increase in the urinary excretion of products mutagenic in the Salmonella/microsome assay. This observation suggests that there is a causality in the association between increased cancer risk and passive-smoking, as was found by other investigators.

Mutagens in urine of non-smoking and smoking workers in an aircraft tyre retreading plant. Skin exposure as a causal factor?

In an aircraft type retreading plant environmental samples taken at several departments showed mutagenic properties. Thursday urine samples of non-smoking and smoking workers showed higher urinary mutagenicity than urine samples collected on Sundays, thus suggesting occupational exposure to mutagenic substances. A relation between urinary mutagenicity on Thursdays and skin contamination measured on Wednesdays was observed. The data suggest that intake through the skin plays an important role in the occupational exposure to mutagenic compounds of rubber workers.

Non-mutagenicity of toluene, o-, m- and p-xylene, o-methylbenzylalcohol and o-methylbenzylsulfate in the Ames assay.

Abstract Toluene, o -, m - and p -xylene, o -methylbenzylalcohol and o -methylbenzylsulfate were assayed for mutagenicity in the Ames assay. These compounds were unable to revert Salmonella typhimurium strains TA1535, TA1537, TA1538, TA98 and TA100, either with or without metabolic activation by S9 mix derived from livers of rats either untreated or induced with Aroclor 1254.

Excretion of benzo[a]pyrene and metabolites in urine and feces of rats: influence of route of administration, sex and long-term ethanol treatment

The urinary and fecal excretion of benzo[a]pyrene (B[a]P) and its main metabolites were studied after oral and intraperitoneal administration of B[a]P to male and female ethanol-treated and non-ethanol-treated rats. After oral administration of B[a]P more mutagenic compounds as well as B[a]P metabolites were found in feces than after intraperitoneal administration. The excretion of B[a]P metabolites in urine and feces after oral administration were maximal at days 1 and 2 whereas after intraperitoneal administration excretion was maximal at days 2 and 3. In males, the amounts of excreted phenolic metabolites in urine and feces were generally higher than in females. The amounts of mutagenic products in urine and feces of males were also higher than in females after intraperitoneal and oral administration of B[a]P. In urine of female rats that received B[a]P intraperitoneally, a decreased excretion of phenolic metabolites was found after ethanol treatment. In feces of both male and female rats, a decreased excretion of 3-OH-B[a]P was found after ethanol treatment. In this study, the influence of sex and administration route on the excretion of B[a]P metabolites was more pronounced than the effect of ethanol treatment.

1-Hydroxypyrene as an indicator of the mutagenicity of coal tar after activation with human liver preparations

Liver S9 fractions were prepared from male Wistar rats, either non-induced or induced with Aroclor 1254 and from 5 human kidney transplant donors. The preparations were compared for their ability to metabolize the premutagens present in coal tar to mutagenic metabolites in the Salmonella mutagenicity assay towards strain TA98. Low levels of mutagenicity of coal tar were seen with human S9 preparations. The differences between the S9 mix of the 5 donors in capacity to activate premutagens were approximately 6-fold. The activation of coal tar by rat liver S9 preparations was higher than by the human S9 preparations. The metabolic conversion of pyrene in coal tar to 1-hydroxypyrene by the same human S9 preparations was determined in a parallel assay. 3 human preparations showed a high correlation between the formation of 1-hydroxypyrene and bioactivation of coal tar to mutagenic metabolites. The slope values of the individual regression lines were equal, suggesting that 1-hydroxypyrene is a good indicator for the activation of premutagens present in coal tar.

Internal exposure of rats to benzidine derived from orally administered benzidine-based dyes after intestinal azo reduction

The role of the rat intestinal flora in the azo reduction of some benzidine-based dyes was studied in vitro and in vivo. The formation of benzidine was measured after anaerobic incubation of direct black 38, direct blue 6 and direct brown 95 in the presence of caecal bacteria in vitro. Benzidine was absorbed from the intestinal tract much better than the parent compounds. Oral administration of direct black 38 or direct brown 95 to Wistar rats results in the urinary excretion of mutagens. After oral administration of these dyes to germ-free Wistar rats no mutagenicity was observed in urine. The present results show that after oral administration, reduction by the intestinal flora should be considered as the first essential step in the biotoxification of benzidine-based dyes.

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.