[Mutagenic effect of cyclophosphan on bone marrow cells of irradiated rats].

The rate of chromosome aberrations in bone marrow cells of male rats was investigated in 24 hours after the cyclophosphan intraperitoneal injection (25 mg/kg). Cyclophosphan was given to rats exposed earlier (15 days, 1, 3, 4, 6 or 9 months before) to X- and gamma-irradiation (400 rads). It was found that preliminary irradiation led to the increase in the mutagenic effect of cyclophosphan as compared to that obtained for intact rats. This effect was demonstrated during 4 months after acute X-irradiation at a dose rate of 70 rads/min and during 1 month after chronic gamma-irradiation at a dose rate of 100 rads/day. Later the effect was shown to disappear in both cases. Chronic irradiation was found to be less efficient in the stimulation of chromosome damages caused by chemical mutagens. The increase of the mutagenic effect of cyclophosphan resulted in the increase of both the number of cells carrying chromosome breaks and the severity of a damage per cell. Different ways of the irradiation effect on the mutagenic action of chemicals are discussed.