Anticlastogenicity of two derivatives of 1,4-dihydroisonicotinic acid in mouse micronucleus test.

Effects of two derivatives of 1,4-dihydroisonicotinic acid (1,4-DHINA) against the monofunctional alkylating agent ethyl methanesulfonate (EMS) were studied in the micronucleus test in (CBA x C57Bl/6(j)) mice. Adult males and pregnant females were treated with an antimutagen (i.p.) and 12h later they were exposed to EMS (i.p.). The frequencies of micronucleated (MN) polychromatic erythrocytes (PCEs) in mouse bone marrow and foetal liver were analysed 6, 12, 18, 24, 30, 36, 48 or 24, 48 and 72 h after the mutagen injection. In adults, the maximum number of MNPCEs was observed 36 or 24h after the EMS administration. In foetuses, which were treated in a maternal organism, such peak was found at 24h. Pre-treatment of mice with the antimutagens 2,6-dimethyl-3,5-diethoxycarbonyl-4-(Na carboxylate)-1,4-dihydropyridine (DHP) and glutapyrone (GP) decreased the yield of MNPCEs in male bone marrow. Having been observed at a peak of MN induction, the anticlastogenic effect of DHP (1/10 LD(50) or 340 mg/kg) reached 30%. DHP at the doses of 0.5-1mM/kg did not affect the EMS-induced frequency of MNPCEs in bone marrow, whereas GP inhibited it at the similar millimolar concentrations. Simultaneously with maternal bone marrow, foetal liver cells were analysed for MNs in the transplacental test. The anticlastogenic effect of DHP (1/10 LD(50)) was found to be more prolonged and higher in females than in males and to average 50%, but this antimutagen was not efficient in foetuses. Both antimutagens did not change the polychromatic/normochromatic erythrocyte (PCE/NCE) ratio as compared with EMS action. Results presented indicate a peak of EMS-induced micronucleated cells in mouse bone marrow 24 or 36 h and in foetal liver 24h after animal treatment. Two 1,4-DHINA derivatives exhibited anticlastogenic activity in adults, but not in foetuses.

Mutagenic effects of dimethyl terephthalate on mouse somatic cells in vivo.

The mutagenic activity of dimethyl terephthalate (DMtP) was evaluated in the micronucleus test in mice. A clear clastogenic effect was obtained at all concentrations studied (0.2-1.0 mmole/kg body weight). The maximum number of micronuclei occurred 24 h after a single intraperitoneal (i.p.) injection. The time-course for the DMtP-induced micronuclei was in agreement with the available data on the rapid excretion of phthalates from the mammalian body. The dose-effect response was best described by a linear equation with a logarithmic component. The emergence of the latter term was related to the toxic effects of DMtP at higher concentrations on bone marrow erythropoietic function. A comparison of the effects induced by DMtP and by methyl nitrosourea indicated that DMtP cannot be considered a strong mutagenic compound. We have compared the sensitivity of the mouse micronucleus test and that of Drosophila dominant-lethal test by contrasting the effects obtained at similar exposure doses. This comparison leads to the conclusion that the micronucleus test is capable of responding to far lower phthalate concentrations than the Drosophila dominant-lethal mutation test. Our results testify to the ability of dimethyl terephthalate to cause genotoxic damages in vivo in both somatic and germinal cells of higher organisms. Thus, the chemical in question may be of potential genetic hazard to man.