The role of biotransformation in the genotoxicity of allylic compounds

Mutagenic and carcinogenic risk of oxygen containing chlorinated C-3 hydrocarbons: putative secondary products of C-3 chlorohydrocarbons and chlorination of water

Oxygen containing C-3 chlorohydrocarbons are secondary products of C-3 chlorohydrocarbons formed during oxidation at air, in the metabolism of pesticides and by chlorination of drinking water. These compounds are mutagenic, genotoxic and carcinogenic. 2-Chloroacroleins are extremely strong mutagens and genotoxins and form 1,N2-cyclic deoxyguanosine adducts. The role of such adducts in mutagenicity and carcinogenicity is discussed.

Mutagenic activity of halogenated propanes and propenes: effect of bromine and chlorine positioning

A series of halogenated propanes and propenes were studied for mutagenic effects in Salmonella typhimurium TA100 in the absence or presence of NADPH plus liver microsomes from phenobarbital-induced rats as an exogenous metabolism system. The cytotoxic and mutagenic effects of the halogenated propane 1,2-dibromo-3-chloropropane (DBCP) has previously been studied in our laboratories. These studies showed that metabolic activation of DBCP was required to exert its detrimental effects. All of the trihalogenated propane analogues were mutagenic when the microsomal activation system was included. The highest mutagenic activity was obtained with 1,2,3-tribromopropane, with approximately 50-fold higher activity than the least mutagenic trihalogenated propane, 1,2,3-trichloropropane. The order of mutagenicity was as follows: 1,2,3-tribromopropane > or = 1,2-dibromo- 3-chloropropane > 1,3-dibromo-2-chloropropane > or = 1,3-dichloro-2-bromopropane >> 1-bromo-2,3-dichloropropane > 1,2,3-trichloropropane. Compared to DBCP, the dihalogenated propanes were substantially less mutagenic. Only 1,2-dibromopropane was mutagenic and its mutagenic potential was approximately 1/30 of that of DBCP. In contrast to DBCP, 1,2-dibromopropane showed similar mutagenic activity with and without the addition of an activation system. The halogenated propenes 2,3-dibromopropene and 2-bromo-3-chloropropene were mutagenic to the bacteria both in the absence and presence of the activation system, whereas 2,3-dichloropropene did not show any mutagenic effect. The large differences in mutagenic potential between the various halogenated propanes and propenes are proposed to be due to the formation of different possible proximate and ultimate mutagenic metabolites resulting from the microsomal metabolism of the various halogenated propanes and propenes, and to differences in the rate of formation of the metabolites. Pathways are proposed for the formation of genotoxic metabolites of di- and trihalogenated propanes and dihalogenated propenes.

Cytochrome P450-dependent bioactivation of prodysmorphogens in cultured conceptuses

These investigations were undertaken to determine the extent to which tissues of cultured rat conceptuses contain cytochrome P450 isoforms in sufficient quantities to significantly influence the capacity of certain chemicals to elicit dysmorphogenic effects in vitro. Investigations with highly sensitive probe substrates/inhibitors and with immunologic methods enabled the detection of at least four separate P450 isoforms in tissues of the visceral yolk sac, ectoplacental cone, and embryo proper. One of the isoforms was identified as P450IA1 and was found to be inducible by polycyclic aromatic hydrocarbons in all three tissues. Other isoforms exhibited properties differing from characterized adult rat hepatic isoforms. Each of the isoforms was detectable in conceptuses on gestational days 10, 11, 12, and 14 and was present in the highest concentrations in the visceral yolk sac. Conceptal P450IA1 catalyzed the conversion of dysmorphogenically inactive 2-acetylaminofluorene to 7-hydroxy-2-acetylaminofluorene, a proximate dysmorphogen. Investigations with microinjections suggested that visceral yolk sac hydroxylation was largely responsible for the bioactivation reaction in vitro. The same isoform exhibited no capacity to influence the dysmorphogenic activity of cyclophosphamide. The results demonstrated that tissues of cultured rat conceptuses may contain P450 isoforms in sufficient amounts to markedly influence the dysmorphogenic activity of substrates of the corresponding isoforms.

Allylic compounds bind directly to DNA: investigation of the binding mechanisms in vitro

The in vitro binding of three allyl compounds, allyl methanesulphonate, allyl bromide and allyl chloride to DNA from salmon sperm was investigated. Kinetic DNA-alkylation measurements revealed significant differences between the strongly alkylating allyl methanesulphonate and allyl bromide with half-life values of 1.5 h and 8.1 h, respectively and the weakly alkylating allyl chloride with a half-life value of 360 h. Five alkylated nucleic bases, 3-allyladenine, N6-allyladenine, N2-allylguanine, 7-allylguanine and O6-allylguanine, could be identified after DNA-alkylation with all three allyl compounds.