Mutagenicity to Mammalian Cells of Epoxides and Other Derivatives of Polycyclic Hydrocarbons

Abstract

The cytotoxicity and mutagenicity of several polycyclic hydrocarbons and their K-region derivatives were tested in a clone of Chinese hamster cells; the production of clones resistant to 8-azaguanine was used as the marker for mutagenesis. In the series related to benz(a)anthracene, the K-region epoxide was highly mutagenic, and the phenol was less mutagenic; the hydrocarbon and cis and trans-dihydrodiols were not mutagenic. Seven resistant clones were isolated and retained their drug-resistance; three of these could be reverted to the wild type. There was no difference in the chromosome numbers among the parent and mutant clones. The results in the methylcholanthrene series were similar to those for benz(a)anthracene. However, in the dibenz(a,h)-anthracene series, the phenol was more mutagenic than the epoxide. 7-Methylbenz(a)anthracene epoxide and 7-bromomethylbenz(a)anthracene were highly mutagenic, 7-bromomethyl-12-methylbenz(a)anthracene was less mutagenic, and the parent hydrocarbons were inactive. These results demonstrate that metabolic activation of polycyclic hydrocarbon is required for mutagenic activity in mammalian cells.In 1950 it was postulated by Boyland (1) that epoxides are intermediates in the metabolism of polycyclic hydrocarbons. Since then, epoxides have been isolated as intermediates in the microsomal hydroxylation of naphthalene (2) and dibenz(a,h)anthracene (3). Moreover, we have shown that K-region epoxides of polycyclic hydrocarbons react with DNA and proteins (4), and are much more active than the corresponding hydrocarbons, dihydrodiols and phenols at producing malignant transformation in cultures of hamster embryo and mouse prostate cells (5). Therefore, it appears highly probable that epoxides are the metabolically activated and ultimate carcinogenic form of polycyclic hydrocarbons, and in common with other ultimate carcinogens (6), are chemically reactive as electrophiles. An alternative mechanism for the metabolic activation of polycyclic hydrocarbons that contain methyl groups has been proposed, which involves carbonium ion formation on the methyl groups (7,8 Because of this chemical reactivity with DNA, it appeared that epoxides of polycyclic hydrocarbons might possess mutagenic activity. Although in the past there has been a very poor correlation between the mutagenic and carcinogenic activities of a number of potent carcinogens, it was recently demonstrated in this laboratory that the ultimate metabolically active forms of the hepatocarcinogenic aminoazo dyes and acetylaminofluorene are mutagenic to bacteriophage T4, whereas the parent compounds and proximal metabolites are not (9). Thus, it appears that one of the major limitations to the development of correlations between the processes of carcinogenesis and mutagenesis is the fact that the metabolic activation that now appears to be a prerequisite for both processes is not performed by many of the bacterial and phage systems used for the assay of mutagenic activity.Recently, considerable progress has been made in d...

An efficient and rapid DNA minipreparation procedure suitable for PCR/SSR and RAPD analyses in tropical forest tree species

“…In this modified method, the use of liquid nitrogen and phenol has Scott and Playfford (1996), grinding samples with liquid nitrogen can produce degradation of DNA. The phenol is suspected to induce the mutagenesis (Huberman et al, 1971). The adaptation of the CTAB extraction procedure also includes: 1) the use of polyvinylpyrrolidone (PVP) to remove the polyphenols and prevent oxidation of the secondary metabolites in plant tissues (as proposed by Ferreira and Grattapaglia, 1995), 2) only one extraction step with chloroform-isoamyl alcohol, and (3) the implementation of RNase treatment after extraction with chloroform and before precipitating the DNA with cold isopropanol (as proposed by Agwanda et al, 1997).…”

The carcinogenicity of polycyclic hydrocarbon epoxides in newborn mice

“…More recent studies with epoxides in 2 in vitro transformation systems (Berwald and Sachs, 1963;Chen and Heidelberger, 1969) have demonstrated that several K region derivatives are more active than the corresponding hydrocarbons in inducing malignant transformation Marquardt et al, 1972;Huberman et al, 1972), but others are not (Marquardt et al, 1974). The epoxides can also act as alkylating agents (Grover and Sims, 1970) and as mutagens (Ames, Sims and Grover, 1972;Huberman et al, 1971;Cookson, Sims and Grover, 1971;Fahmy and Fahmy, 1973). Rapidly dividing cell populations, like those used in the in vitro transformation systems, might be expected to be more susceptible to reactive carcinogens, like epoxides, than mitotically inactive tissues if reactions with cellular constituents at a particular stage of the cell cycle are important (Bertram and Heidelberger, 1974;Marquardt, 1974).…”

Caffeine inhibits excision of 7-bromomethylbenz (a) anthracene-DNA adducts from exponentially growing but not from stationary phase Chinese hamster cells

“…7-Bromomethylbenz(a)anthracene (7-BMBA) is a direct acting nucleotoxin which exhibits carcinogenicity in mice (1,2,3) cytotoxicity and mutagenicity towards mammalian cells and bacteria (4,5,6), is effective in inactivating bacteriophage (7) and causes chromosome breakage in cultured Chinese hamster cells (8). 7-BMBA-DNA adducts are chemically stable under physiological conditions (9) and are removed from the DNA of hamster cells (10), and human cells (11) by an excision repair mechanism.…”