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The effect of beta-carotene on the frequencies of micronuclei (MN) induced in cytochalasin blocked binucleated Chinese hamster ovary cells (CHO) by a bifunctional alkylating agent mitomycin C (MMC), a monofunctional alkylating agent methyl methanesulphonate (MMS) and a radio-mimetic agent bleomycin (BLEO) was investigated. Four different modes of application of the combination of clastogens and beta-carotene were examined (pre-treatment, simultaneous treatment, pre- +simultaneous treatment and post-treatment). The results obtained showed no effect of beta-carotene on the frequencies of MN induced by MMS, a slight but not statistically significant reduction of MMC-induced MN only when beta-carotene was used in low concentrations (0.25 and 0.5 microM) and a potentiation of the clastogenicity of bleomycin by beta-carotene in three of the treatment regimes utilized, post-treatment being ineffective. On the basis of these results it can be concluded that the effect of beta-carotene on clastogenesis induced by chemicals depends on the type and mechanism of action of the clastogen used as well as the treatment protocol employed.

beta-Carotene exhibited dose-dependent anticlastogenic effects on aberrations induced by the direct-acting mutagens thio-TEPA, methyl methanesulfonate and busulfan in the in vivo chromosome aberration test (bone marrow cells, Chinese hamsters). No effect was seen when retinol was used. Apparent differences in the action of beta-carotene on aberrations induced by the three applied mutagens may be due to differences in the solubility of the compounds and to the different routes of administration.