M. Lambottevandepaer

Effect of several factors on the liver extract mediated mutagenicity of acrylonitrile and identification of four new in vitro metabolites.

The mutagenicity of acrylonitrile (ACN) was tested with Salmonella typhimurium TA1530 after a preincubation period of the chemical with a rat liver post-mitochondrial fraction in liquid medium. Several pretreatments were applied to the animals before the preparation of the liver fractions and different compounds added to the incubation mixture, which were shown to modify the liver mediated mutagenic activity of ACN. Four metabolites: cyanoacetic acid, cyanoethanol, acetic acid and glycolaldehyde were identified after incubation of ACN with the rat liver homogenate. From both sets of results, an in vitro metabolic scheme is proposed to ACN, which postulates the intermediate formation of a radical species and an epoxide.

Mutagenicity of Urine From Rats and Mice Treated With Acrylonitrile

Urines collected from rats and mice treated with acrylonitrile (ACN) were mutagenic towards Salmonella typhimurium strain TA 1530 in the absence of a metabolic activation system. When assayed in the presence of a liver S9 mix, this activity was suppressed when the urines were obtained from acrylonitrile treated rats, and decreased when these urines were collected from acrylonitrile treated mice. Pretreatment of the animals with phenobarbital abolished the direct mutagenicity of urines from acrylonitrile treated rats, and reduced that observed with mice urines. Addition of beta-glucuronidase to the incubation mixtures enhanced the mutagenicity of the urines from both phenobarbital untreated and treated rats and mice injected with acrylonitrile.

Identification of two urinary metabolites of rats treated with acrylonitrile; Influence of several inhibitors on the mutagenicity of those urines

Urines collected from rats injected with acrylonitrile (ACN) were mutagenic towards Salmonella typhimurium TA1530; this activity was reduced when the animals were pretreated by pyrazole (inhibitor of alcohol dehydrogenase) and suppressed after pretreatment either by CoCl2 and SKF 525-A (inhibitors of the mixed-function oxidases system) or by trichloroacetonitrile (radical trapping agent). On the other hand, two urinary metabolites (cyanoethanol and cyanoacetic acid) have been detected by gas chromatography. One possible scheme for the in vivo metabolism of ACN is presented which postulates the intermediate formation of a radical species and of an epoxide.

Liver extract mediated mutagenicity of acrylonitrile.

The mutagenic activity of acrylonitrile vapours towards Salmonella typhimurium strains strictly depends upon the presence of a liver postmitochondrial fraction. The reversion rate varies according to the animal species from which the S9 fraction is obtained as well as to the pretreatment of the animals. The comparatively weak activating effect of the microsomal fraction and the inability of both SKF525A and carbon monoxide to inhibit the S9 mediated mutagenicity of acrylonitrile (ACN) suggest that the cytochrome P-450-dependent monooxygenases do not play a major role in the metabolic activation of ACN into a mutagenic intermediate (s).

Mutagenicity of Styrene in the Salmonella-typhimurium Test System

The mutagenic activity of styrene was investigated by incubating the strains of Salmonella typhimurium in gaseous atmospheres. The sensitive strains were TA1530, TA1535 and TA100. In that method, styrene regularly showed a mutagenic activity in the presence of a fortified liver post-mitochondrial fraction. The mutagenic activity remained weak. Moreover, it seemed that a volatile mutagenic intermediate was formed metabolically during the assays; its identity remains unknown.

Influence of Experimental Factors on the Mutagenicity of Vinylic Monomers

The results obtained by testing the mutagenicity of several vinylic monomers, styrene, butadiene, acrylonitrile, vinyl chloride on strains of Salmonella typhimurium in various experimental conditions, modes of incubation, and in the presence of different metabolic activating systems, demonstrate that these parameters have a variable effect on the mutagenic potency of those monomers.

Role of Glutathione in Liver-mediated Mutagenicity of Acrylonitrile

The mutagenic activity of acrylonitrile (ACN) towards the Salmonella typhimurium strain TA1530 was evaluated after a short preincubation time in liquid medium in the presence of microsomes, cytosolic fractions and post-mitochondrial fractions of liver from untreated and phenobarbitone (PB)-pretreated rats and mice. The effect of the presence of glutathione (GSH) was also examined. GSH enhanced the microsomal-mediated mutagenicity of ACN; that effect was abolished in the presence of CO. The effect of GSH was usually greater after pretreatment by phenobarbitone. Other sulfhydryl compounds induce a weaker mutagenic activity than GSH. These observations support the hypothesis of a mediated formation of a mutagen involving GSH, but the adduct between ACN an GSH was not mutagenic.

Biochemical effects of acrylonitrile on the rat liver, as influenced by various pretreatments of the animals.

Abstract Acrylonitrile is extensively used in the synthesis of plastics, some of which are used for the packaging of food and beverage. A single dose of AN causes an increase in serum lactate and sorbitol dehydrogenase levels, as well as a decrease of liver cytochrome P-450 content and microsomal aldrin oxide synthetase activity. Those effects are prevented by pretreatments of the animals with either inducers of the mixed function oxidases or L-cysteine; diethylmaleate pretreatment enhances the increase of the soluble enzyme levels.

Styrene induced modifications of some rat liver enzymes involved in the activation and inactivation of xenobiotics.

Abstract Rats were injected intraperitoneally with single doses of styrene. Its effects on the kinetic parameters of liver microsomal monooxygenases and epoxide hydratase were investigated. The results were compared with those produced either by ethylbenzene, the vinyl-saturated analog of styrene or by phenobarbital and 3-methylcholanthrene, the classical inducers of those enzymes. The biochemical modifications were correlated with the altered ability of homogenates obtained from similarly pretreated rats to activate benzo(a)pyrene into intermediates mutagenic towards Salmonella typhimurium . Administration of styrene or 3-methylcholanthrene decreased the K m , of benzo(a)pyrene hydroxylase and aldrin epoxidase; styrene, but not 3-methylcholanthrene, decreased the K m of styrene oxide hydratase; none of the two compounds modified the K m of styrene epoxidase. Pretreatment of the rats by styrene or 3-methylcholanthrene enhanced the S 9 mediated mutagenicity of benzo(a)pyrene several-fold, when compared to the mutagenic response mediated by liver preparations from control rats. Phenobarbital and ethylbenzene did not modify either the K m of the investigated enzymes or the liver-mediated mutagenicity of benzo(a)pyrene.

Population Monitoring for Genetic-damage Induced By Environmental Physical and Chemical-agents

The short-term tests performed in vitro on different systems, from phage to human cells, or in vivo, on laboratory animals, allow only a qualitative estimate of the action of mutagenic agents, and the extrapolation of such experimental results to man may encounter many difficulties.Direct biomonitoring of populations exposed to chemicals could represent a more realistic approach for an evaluation of the hazards to man. Certain methods are still under development. Nevertheless, other ones can already by used routinely, e.g. the cytogenetic observations on peripheral blood lymphocytes and the Ames test for mutagenic substances in urine, and can provide useful suggestions how to set threshold limits for chemical substances encountered in the working environment.