The effect of unilateral nephrectomy on the subsequent radiation response of the pig kidney.

The left kidney of 14 Large White female pigs, approximately 14 weeks of age, was surgically removed. Thirty weeks after unilateral nephrectomy (UN) the remaining kidney was irradiated with a single dose of between 11.9 and 15.6 Gy of 60Co gamma-rays; three pigs received sham irradiation. Following irradiation glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and haematocrit (Hct) were determined for up to 48 weeks after irradiation. Irradiation resulted in a dose-dependent decline in GFR, evident 8 weeks after irradiation. This was followed by a gradual improvement in GFR, although after doses of 14.0 Gy GFR remained below control values throughout the study. A similar pattern of response was seen in terms of ERPF, but this was not dose-related. Doses of greater than or equal to 14.0 Gy also caused a significant reduction (p less than 0.001) in Hct within 4-8 weeks. Minimal levels were evident 16 weeks after irradiation; Hct then increased, but remained below preirradiation values. Dose-effect curves were obtained by determining the percentage of irradiated kidneys which showed a greater than or equal to 50% reduction in GFR and ERPF, fitted by probit analysis, and ED50 values (+/- SE) were calculated for each parameter. The ED50 values for GFR and ERPF were 14.49 +/- 0.27 Gy and 12.56 +/- 0.98 Gy, respectively. These values were not significantly different from those obtained from intact age-matched pigs in which the right kidney alone was irradiated; UN did not compromise or alter the radiation response of the kidney to irradiation. However, the ED50 values obtained for the UN pigs were significantly greater (p less than 0.001) than the values of 9.76 +/- 0.17 Gy and 6.19 +/- 0.93 Gy, seen for GFR and ERPF in intact age-matched pigs in which both kidneys were irradiated. Thus although both experimental situations involved irradiating the entire renal tissue, the relative radiosensitivity of the kidneys varied considerably. These findings show that the radiosensitivity of the pig kidney can vary markedly, depending on the physiological status of the kidney at the time of irradiation.