[The cytofluorimetric analysis of the nuclei in the regenerating rat liver in the late periods after x-ray irradiation].

The flow cytofluorimetric method allowed to show that intact liver nucleus population of adult (6 months) rats consists of discrete ploidy classes (2c, 4c, 8c and 16c+), from which the diploid class was approximately a half of the total nuclei. Thirty days after the wholebody X-ray irradiation with a dose of 2 Gy, the percentage frequency of each nuclear class was statistically unchanged. However, the polyploidization level of the total nuclear population increased. Partial hepatectomy induces an entering into mitotic cycle (maximum S-phase; 22 h after operation) of the most of the hepatocyte nuclei in both irradiated and unirradiated animals. With that the relative number of nuclei in S-phase decreases in geometric progression according to increasing of ploidy class. In regenerating liver of irradiated rats in comparison with that of unirradiated ones, the greater part of nuclei enters into the mitotic cycle at the expense of di- and especially tetraploid nuclei.