[Mitotic activity and chromosome aberrations in regenerating rat liver following x-ray irradiation]

Changes in the mitotic index (MI), the ratio of the metaphase to prophase number (M/P) and the chromosome aberration frequency in the regenerating rat liver were followed after single irradiation with exposures 77.4; 154.8 and 258 mC/kg (300, 600, 1000 R). The animals were partially hepatectomized immediately after irradiation and from the 18th hour to the 21st day after the treatment they were tested simultaneously with non-irradiated control animals. Irradiation resulted in approximately 6-hour delay in initiation of the mitotic activity in the regenerating liver. The inhibition extent depended on the magnitude of the exposure. A single exposure 77.4 mC/kg caused a 15% decrease in the mitotic activity, exposures 154.8 mC/kg and 258 mC/kg a 39% and 76% decrease, respectively, compared with control animals. M/P ratio in the regenerating liver in control and irradiated animals (77.4 and 154.8 mC/kg) manifested cyclic changes during the first 3 days. M/P values were about the highest level in irradiated animals depending on the exposure. postmetaphase figures in animals exposed to 77.4 mC/kg were aberrant in 50%. In animals exposed to 154.8 and 258 mC/kg, the percentage of chromosome aberrations ranged within 80-100%.