INFLUENCE OF A LOW-PROTEIN DIET ON RADIATION NEPHROPATHY IN THE PIG

Nine mature, approximately 45-week-old pigs, were fed a standard diet (SD) containing 16% protein; 10 pigs were fed an isocaloric low protei n (LP) pig feed containing 4% protein 2 weeks prior to and 16 weeks af ter renal or sham-irradiation. The pigs then received the SD for a fur ther 4 weeks. Both kidneys of seven pigs fed the LP diet, and six pigs fed the SD, were irradiated with a single dose of 9.8 Gy of Co-60 gam ma-rays. The remaining pigs received sham-irradiation. The individual kidney glomerular filtration rate (GFR), effective renal plasma flow ( ERPF), and the haematocrit were serially measured before and up to 20 weeks after irradiation. The radiation-induced reduction in mean indiv idual kidney GFR, expressed as either absolute values or as a percenta ge of the respective sham-irradiated controls, was significantly great er in pigs fed the SD compared with pigs fed the LP diet (p<0.05). In contrast, the radiation-induced reduction in mean individual kidney ER PF, expressed as absolute values, observed in pigs fed the SD was not significantly different from that seen in pigs fed the LP diet. Howeve r, if these data were expressed as a percentage of the respective sham -irradiated controls, then a significantly greater reduction in ERPF w as seen in pigs fed the SD compared with pigs fed the LP diet (p<0.001 ). Morphological analysis of renal tissue removed 20 weeks after irrad iation showed that the extent and severity of the glomerular lesions s een in pigs fed the SD were significantly reduced in pigs fed the LP d iet. Thus dietary protein restriction appears to reduce some of the si gns of radiation nephropathy in the pig.