Cytokinetics of rat tracheal epithelium stimulated by mechanical trauma

Mild abrasion of rat tracheal epithelium results in irreversible damage to the superficial cells and stimulates the viable basal cells to participate in a nearly synchronous wave of DNA synthesis and mitosis. For the growth population as a whole, DNA synthesis started at 14 hr after injury and persisted for 16 hr. The duration of S in individual cells was determined autoradiographically by identifying the time at which a second pulse of DNA precursor (14C-TdR) was no longer incorporated by cells labelled with 3H-TdR at the onset of S. S was found to be 8-9 hr long. It was also determined that cells entering S at later times synthesized DNA for the same 8-9 hr period. TG2 was calculated to be 2 1/2-3 1/2 hr by subtraction of TS and 1/2TM from the period from onset of DNA synthesis to metaphase. By making a second denuding lesion adjacent to the first injury, the cells were stimulated through at least another period of S. At the peak of the second wave of DNA synthesis (50 hr after injury) 14C-TdR was present in the same cells which had incorporated 3H-TdR administered at the mid-point of the preceeding synthetic phase. The 28-hr interval between these two peaks of synthesis is the measure of cell cycle duration for these regenerating tracheal epithelial cells.