F. Poncelet

Mutagenicity of styrene and styrene oxide

Abstract Incubation of S. typhimurium strain TA 1535 with styrene increased the number of his + revertants/plate in presence of a fortified S9 rat-liver fraction. Styrene was also highly cytotoxic for Salmonella cells. Styrene oxide, the presumed first metabolite, had a mutagenic effect towards strains TA 1535 and TA 100 both with and without metabolic activation. Styrene is probably mutagenic because it is metabolized to styrene oxide.

Identification and quantitation of 1,2-epoxybutene-3 as the primary metabolite of 1,3-butadiene

Abstract 1,3-Butadiene was incubated in the presence of rat liver microsomes supplemented with an NADPH-generating system. One of the major metabolites of butadiene was found to be 1,2-epoxybutene-3, which was analysed by electron-capture gas—liquid chromatography after its derivatization with pentafluorophenylhydrazine. The effects of variation of several incubation parameters and of different pretreatments of the animals on its formation kinetics were evaluated.

Mutagenicity of butadiene and butadiene monoxide.

Abstract Incubation of S. typhimurium strains TA1530 and TA1535 in the presence of gaseous butadiene increased the number of his+ revertants/plate. This mutagenic effect occured in absence of fortified S-9 rat liver fraction. In its presence, the mutagenic effect seemed to be dependent on its composition. With butadiene monoxide, a reversion to histidine prototrophy was obtained without metabolic activation with strains TA1530, TA1535 and TA100. Butadiene monoxide might be a possible primary metabolite of butadiene.

The mutagenicity of butadiene towards Salmonella typhimurium.

Gaseous butadiene (BUT) was mutagenic towards S. typhimurium strain TA 1530 when the incubation mixture was supplemented with a NADPH-fortified rat liver microsomal preparation; mutagenicity increased with the dose. A significant mutagenic effect was similarly observed when the petri dishes, containing the bacteria but no metabolic activation system, were incubated in the presence of butadiene, in a desiccator in which plates containing the S-9 rat liver fraction had been placed. This indirect mutagenic effect was attributed to the formation, by the S-9 mix, of volatile intermediate(s) that migrated and induced mutations in neighbouring bacteria.

Mutagenicity of acrylonitrile

Incubation of Salmonella typhimurium strains in an atmosphere of 0.2% gaseous acrylonitrile increased the numbers of his+ revertants/plate only in the presence of a fortified S9 liver fraction. The mutagenic effect was particularly pronounced with strains TA1530, TA1535 and TA1950 and much weaker with strains TA100, TA98 and TA1978. The results of bacterial fluctuation tests confirmed the necessity of the presence of S9 mix and showed the particular sensitivity of TA1530. The reversion rate varied with the S9 mix composition, the animal species utilized and the type of pretreatments applied to the animals. The mutagenicity of acrylonitrile in S. typhimurium is therefore microsome-mediated and is particularly discernable with strains sensitive to base-substitution mutagens.

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.

Genetic-effects of Chlorinated Anilines and Azobenzenes On Salmonella-typhimurium

The mutagenicity of 19 herbicide-derived chlorinated azobenzenes and structurally related chlorinated anilines and nitrobenzenes was assayed towards several strains ofS. typhimurium, using the plate incorporation method and the fluctuation test, in the presence or in the absence of liver post-mitochondrial fractions, in aerobic and anaerobic conditions.Positive results were obtained with 4,4′-dichloroazobenzene, 4,4′-dichloroazoxybenzene, 3,4-dichloronitrobenzene and, to a much lesser extent, with 3,4,3′,4′-tetrachloroazobenzene. No mutagenic effect was observed with 2,3,7,8-tetrachlorodibenzo-p-dioxin in any condition.

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.

Mutagenicity of acrylonitrile in mouse

The capacity of acrylonitrile (ACN) to produce chromosome aberrations in mammals was studied in somatic and germ cells of male NMRI mice. Induction of chromosome aberrations was followed in bone marrow cells 6, 18, 24, 48 and 72 h after an i.p. injection of 20 or 30 mg/kg acrylonitrile, and polychromatic erythrocytes were examined for the presence of micronuclei 24, 30 and 48 h after injection. The dominant lethal test served to detect chromosome aberrations in meiotic and postmeiotic male germ cells. All the tests utilized yielded negative results, so that it may be concluded that acute treatment with acrylonitrile has no clastogenic effects on male mouse cells in vivo.

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.