Nephropathy in the mature pig after the irradiation of a single kidney: A comparison with the immature pig

Abstract

The right kidney of 11 mature 10-month-old Large White female pigs was irradiated with single doses of 9.8–14.0 Gy of 60Co γ rays. Individual kidney glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured using 99m-Tc-DTPA and 131I-hippuran renography for periods up to 24 weeks after irradiation. Renal function was assessed either as a functional index, FI (FI = irradiated /unirradiated kidney function), or as the individual kidney GFR and ERPF. The radiation-induced changes after the irradiation of a single kidney (unilaterally irradiated—UI) of mature pigs were compared with those previously observed in 14-week-old immature pigs. Irradiation resulted in a dose-dependent reduction in the FI for both GFR and ERPF. However, these reductions were significantly less than those previously seen in immature pigs. Within 2 weeks of irradiation GFR increased in both the irradiated and the unirradiated kidneys in each animal, compared with unirradiated age-matched control kidneys. No marked changes in renal hemodynamics were seen in mature animals after a single dose of 9.8 Gy. This was in marked contrast to the pronounced reduction in the GFR and ERPF in the irradiated kidney previously observed in immature animals irradiated with an equivalent single dose of X rays. After higher doses, the irradiated kidney in mature pigs showed a dose-dependent reduction in GFR and ERPF. However, the extent of this reduction was significantly less than that seen in immature animals. There was no apparent difference in the response of the unirradiated kidneys in mature or immature pigs. The EDS 50 values, based on a probit fit to the data for the proportion of functional tests in which the irradiated kidney showed a ≧50% reduction in GFR or ERPF, were higher in the mature animals; for example for ERPF the EDS 50 values were 11.76 ± 0.28 Gy and 7.67 ± 0.34 Gy for mature and immature animals, respectively. Thus, the UI kidney in mature pigs appears to be less radiosensitive than the UI kidney in immature animals.