A short low-level exposure to metavanadate during a cell cycle-specific interval of time is sufficient to permanently derange the differentiative properties of Mel cells.
Mouse erythroleukemia (Mel) cells have a cell cycle-dependent high sensitivity to chemical and physical mutagens. This report shows that a 5 h exposure to 0.1 or 0.01 microg/ml metavanadate during the initial period of erythroid differentiation induction was sufficient to permanently damage the ability of treated Mel cells and their progeny to undergo erythroid differentiation, without affecting cell viability and proliferation. Conversely, a 5 h pulse of metavanadate at 1 or 10 microg/ml inhibited both differentiation and cell proliferation. The cell cycle-dependent period of mutagenesis was essential for fixation of damage in the cell genome and the progeny of the cells treated with 0.1 or 0.01 microg/ml metavanadate stably inherited an impaired capacity to differentiate. The efficiency of the DNA repair synthesis machinery during the specific period of exposure of Mel cells seemed directly involved in damage fixation. In fact, the mutagenic effects of a 0.1 microg/ml metavanadate pulse was further increased in the presence of 1 mM hydroxyurea, an inhibitor of DNA repair synthesis. In contrast, 5 microg/ml vanillin, an antimutagenic agent that stimulates repair, completely restored the capacity of progeny of cells treated with 0.1 microg/ml metavanadate to complete differentiation. Determination of [(3)H]deoxythymidine in acid-insoluble DNA indicated that incorporation was stimulated by metavanadate alone and was further increased by metavanadate plus vanillin; conversely, incorporation of thymidine was reduced in the presence of hydroxyurea. The capacity of metavanadate to permanently damage Mel cell erythroid differentiation appeared to depend on the cell cycle-related efficiency of the DNA repair systems, activated to correct the induced alteration, rather than on a specific concentration.