Cell Cycle Analysis and Stimulation of Rat Kangaroo Cells (PtK2) after Pulse Labeling

Abstract

The phases of the cell cycle of Potorous tridactylus (PtK₂) cells were determined in vitro by analysis of labeled mitoses for 37-½ hours after a tritiated thymidine pulse. The mean duration of DNA synthesis (t_S) was 8 h. The mean duration of the gap phase before appearance of labeled mitoses was 5 h. Whereas the duration of the cell cycle (t_C) based on analysis of labeled mitoses was 30 h, the doubling time (t_D) derived from cell counts in the same cultures was only about 23 h. The analysis of the indices of labeled nuclei and mitoses suggests a stimulation of cells at the time of pulse labeling, which was maximal after beginning of the gap phase before DNA-synthesis, and possibly caused the observed difference between t_C and t_D.