[Mutations of resistance to 6-thioguanine following roentgen irradiation and subsequent treatment with cytosine arabinoside combined with hydroxyurea in Chinese hamster cells in the G1 phase].

A study was made of the effect of two-hour treatment of Chinese hamster cells with cytosine arabinoside (AraC) combined with hydroxyurea (HU) at the G1 phase of the cell cycle on lethal and mutagenic effects of X-radiation (50 to 400 cGy). The inhibitors were shown to increase a spontaneous mutation level of the resistance to 6-thioguanine: this increase augmented by 3 times as the time the treatment increased from 1-2 to 6 h. However, while sharply enhancing the inactivating effect of X-radiation (the enhancement coefficient was 2.6) Arac+HU caused an additive, or a somewhat lesser, effect as estimated by the yield of mutations. It is suggested that AraC combined with hydroxyurea fail to modify the radiation-induced premutation damages.