Repair of x-ray-induced DNA damage in rat cerebellar neurons and brain tumor cells

The in vivo DNA repair kinetics of rat cerebellar neurons and intracerebral 9L tumor cells were simultaneously assessed in the same rat after a single 5000-rad dose of x rays using an alkaline sucrose gradient sedimentation technique in slow reorienting zonal rotors. An x-ray dose of 5000 rad produced the same amount of DNA damage in both 9L tumor cells and cerebellar neurons. However, at every repair time studied up to 24 hr, the tumor cell DNA was always repaired to a greater extent than the neuronal DNA. Restoration of the chromosomal DNA structure to its unirradiated state in intracerebral 9L tumor cells and in cerebellar neurons required 24 and 38 hr, respectively. Thus, nondividing neurons appear to repair their radiation-induced DNA damage to the same extent as the dividing tumor cells, but they do so at a slower rate