Todralazine influence upon the mutagenicity of some direct- and indirect-acting mutagens

Assessment of the relationship between the antimutagenic action of riboflavin and glutathione and the levels of antioxidant enzymes

In this study the role of antioxidant enzymes on the antimutagenic actions of riboflavin and reduced glutathione against mutagenic potentials of 4-nitroquinoline 1-oxide and mitomycin C have been investigated. For this purpose the activities of catalase and superoxide dismutase enzymes have been determined in Salmonella typhimurium TA102 and TA100 strains preincubated with different combinations of 4-nitroquinoline 1-oxide, mitomycin C, riboflavin and reduced glutathione for thirty minutes. Also in part of the same samples, the mutagenicity has been determined for each combination of chemicals by using Salmonella preincubation test. The correlation between the levels of antioxidant enzymes and mutagenicity and antimutagenicity has been investigated.While riboflavin displayed a weakly antimutagenic effect on 4-nitroquinoline 1-oxide mutagenicity in TA102 and TA100 (0.25, 0.35 inhibition respectively), it did not have any effect on the strong mutagenicity of mitomycin C in both strains. Reduced glutathione, a well known antioxidant, had no antimutagenic effect against the mutagenicity of both compounds in TA102 and TA100 strains. The antioxidant enzymes, catalase and superoxide dismutase, seemed to have no direct effect on the antimutagenic action of riboflavin and mutagenic action of 4-nitroquinoline 1-oxide and mitomycin C because no change in the activities of catalase and superoxide dismutase was detected in relation to antimutagenicity of riboflavin and mutagenicity of 4-nitroquinoline 1-oxide and mitomycin C in both strains. It should be noted that many antimutagens have more than one mechanism of action and their effect depends on the mutagens being tested.

Comparison of alkaline single cell gel (Comet) and peripheral blood micronucleus assays in detecting DNA damage caused by direct and indirect acting mutagens

The alkaline single cell gel (SCG) or 'comet' and peripheral blood micronucleus (pbMN) assay have been used to compare the effects of the direct acting mutagens, methyl methanesulfonate (MMS) and N-nitroso-N-methylurea (NMU), and the indirect acting mutagens, benzo[a]pyrene (BAP), cyclophosphamide (CP) 9, 10-dimethyl-1,2-benzanthracene (DMBA), and mitomycin C (MMC) in an inbred house mouse (Mus domesticus) strain. The alkaline SCG assay was able to detect DNA damage from direct acting mutagens. However, it appears that, even at the highest concentrations tested, the SCG assay was not able to detect DNA damage caused by 3 of 4 indirect acting mutagens tested. The exception was BAP. The pbMN assay was sensitive to DNA damage caused by both groups of mutagens. Multiple injections did not increase the sensitivity of the SCG assay to the indirect acting mutagen CP. Further, simultaneous injections of CP and MMS, in one experiment, resulted in significantly lower (p < 0.05) average DNA ratios and micronucleated polychromatic erythrocyte counts than those obtained after treatment with MMS alone. Although the SCG assay has been shown to be sufficiently sensitive to detect DNA damage caused by both direct and indirect acting mutagens in deermice (Peromyscus maniculatus) and bullheads (Ameiurus nebulosus), similar results are not seen in the inbred house mouse strain tested.

Antimutagenic activity of alkylresorcinols from cereal grains

Alkylresorcinols, natural amphiphilic compounds commonly found in cereal grains, markedly decreased mutagenic activity of four standard mutagens examined in the Ames test. The effect was the strongest in the case of indirect-acting mutagens, benzo[a]pyrene and 2-aminofluorene. In the case of direct-acting mutagens, daunorubicin and methyl methanesulfonate, the diminution of the mutagenic activity by the alkylresorcinols was smaller but still noticeable. In the Sister Chromatid Exchanges test (SCEs) with cultured in vitro human blood-derived lymphocytes, a significant decrease of SCEs frequency induced by benzo[a]pyrene was observed in the presence of alkylresorcinols. These preliminary results seem to be important in the aspect of possible antimutagenic and anticarcinogenic potency of alkylresorcinols found in cereal grains.