[The kinetics of the transition to DNA synthesis in the cell cycle of sister cells of the ESK line in culture].

The proliferation kinetics of a cultured pig embryo kidney cell line, PK, was studied by time lapse cinemicrography and 3H-TdR autoradiography. The duration and variability of all phases of the cell cycle was estimated. Evidence is presented that the variation in the cell cycle transit time of both unrelated and sibling cells results mainly from the variation in transit of G1-phase. These results indicate that the kinetics of the entry of cells into the S-phase represents the first order kinetics and does not contradict the transition probability model of cell cycle control. Analysis of the labeling pattern of sister cells reveals a clear correlation of the sister cells G1 transit time.