[Duration of the mitotic cyle of mouse liver cells at different stages of carcinogenesis induced by ortho-aminoazotoluene].

Orthoaminoazotoluol was administered to mice for a period of 9 months. The duration of the G2-and S-periods of the mitotic cycle determined by the autoradiographic method, and mitotic duration--by the stathmokinetics technique with the use of colchicine in the intact liver, the cells of the adenoma nodes, and primary hepatomas. The duration of the S-period of the intact hepatocytes and adenoma nodes proved to be equal (13.8 hours, respectively). As to the primary hepatoma cells--it decreased to 12.8 hours. The duration of the G2-period showed no essential change during the carcinogenesis, and was equal to 2.2--2.7 hours. An average mitotic duration in the course of 24 hours was also constant and was approximately equal to 1 hour. A rise in the number of mitoses and PNA-synthesizing cells in the hepatomas occurred as a result of entering in mitosis and the S-period of a greater number of cells, but not as a result to prolongation of the duration of the S-and M-periods of the mitotic cycle.