Recovery of rat lens epithelial cells after total or partial X-irradiation

Irradiation of whole lenses interferes with the normal mitogenic response of lens cells to stimulation by mechanical wounding. Radiation exposure causes a delay and partial suppression of cells entering the S phase of the cell cycle. When cells are irradiated 1 day before wounding, DNA synthesis begins 20 hr after wounding and peaks 10 hr later with 20% cell labelling. The return to a normal wound response is gradual when the time interval between irradiation and wounding is lengthened. By 28 days, essentially complete recovery of the wound response occurs. Examination of the beginning of mitosis shows a similar pattern of recovery. When half of the lens is irradiated 1 day before wounding, delay and suppression of the wound response in the irradiated half of the lens epithelium is observed. However, if 4 days elapse between irradiation and mechanical wounding, complete recovery of cells responding to the mitogenic stimulus occurs. Cells of the shielded half of the lens appear to compensate for the reduced number of irradiated cells entering S phase so that peak labelling of shielded cells is 70% compared with 50% for control lens cells. An evaluation of mitotic figures confirms faster recovery of the entire lens when only half the lens is irradiated. Complete recovery of the cellular response of partially irradiated lenses occurs in 4 days in contrast to almost 28 days for wholly irradiated lens.