Age-related cell cycle kinetics in the stimulated mouse vaginal epithelium

The cell cycle of the vaginal epithelium of castrated mice after an estrogenic stimulation has been investigated in adult and in aged animals. In aged animals, some cells (at least the first entering S-phase in response to the stimulus) remain able to react and to complete the prereplicative phase as fast as in younger animals. The dose of the stimulus has an all-or-nothing effect on the triggering of the response, and the critical dose value does not change with age. The only age effect suggested here is a lower proportion of cells synthesizing DNA in response to the stimulus, indicating an enhanced variability in the responding times of the individual cells.