Effect of Whole-Body X-lrradiation on Renal Compensatory Hypertrophy

Studies of the effects of X-irradiation on regenerating rat liver have shown that a single sublethal dose administered either before or within 15 hours after partial hepatectomy results in a delay of several hours in the onset of the regenerative response (1, 2). In the kidney undergoing the compensatory hypertrophy which follows unilateral nephrectomy, Rosen and Cole (3) have reported that 690 R of whole-body X-irradiation given to female mice 3 hours after operation depressed the response to unilateral nephrectomy, but that the same dose of X-rays given either 1 hour before or 48 hours after operation was without effect. This suggested that there was a particularly radiosensitive period of renal compensatory growth during the first few hours after unilateral nephrectomy. The experiments reported here are an attempt to clarify the situation regarding the time-specificity of the effect of a single dose of 600 to 700 R of whole-body Xirradiation on the growth of the remaining kidney after unilateral nephrectomy in the female C57 black mouse. By comparison of the weight and DNA content of the right kidney at sacrifice with values for the left kidney removed at operation 21 days earlier, the effect of a radiation dose given between 18 hours before and 51 hours after operation has been evaluated. Also, by autoradiography using tritiated thymidine as label, the rates of DNA synthesis in kidneys of unirradiated and irradiated animals have been compared at 2 and 4 days after operation.