Search

Concern about radiation induced nephropathy results in a dose limiting constraint in some applications of radiation therapy. An understanding of the etiology of radiation therapy. An understanding of the etiology of radiation nephropathy is essential if attempts to alter the time course or extent of the pathology are to be successful. In an attempt to gain a better understanding of this disease process, and to see if it could be altered by dietary manipulation, young adult male Sprague-Dawley rats were unilaterally nephrectomized, after which the remaining kidney was exteriorized and exposed to 14 Gy of X rays. Non-irradiated control animals had their remaining kidney exteriorized for a comparable length of time. Five days after irradiation, the animals were switched from standard lab rations to isocaloric diets of differing protein content. Diets used included 4%, 20% and 50% protein and the 4% and 20% diets given in combination with 0.9% NaCl drinking water. For all the diet groups, irradiated animals had median survival times shorter than their corresponding non-irradiated controls. Within the irradiated groups, the ranking of the median survival times was: 4% + 0.9% NaCl greater than 4% greater than 20% + 0.9% NaCl = 20% greater than 50%. The differences in survival among the irradiated groups were significant at the 0.01 level. These data indicate that kidney response to irradiation can be altered by manipulation of dietary protein levels. Such information may have clinical application.

Immediately following unilateral nephrectomy the remaining kidney of juvenile male Sprague-Dawley rats was sham irradiated or irradiated to doses of 14-30 Gy. Following irradiation the animals were placed on isocaloric diets of either 20 or 4% protein. Median life spans for the animals on the low protein diet were significantly increased compared to the median life spans on the 20% protein diet. Serum urea nitrogen (SUN) levels were periodically measured in rats from each of the experimental groups. SUN levels in the irradiated rats fed the 20% protein diet increased significantly over unirradiated controls as a function of time. In contrast animals fed the 4% protein diet showed no significant changes in SUN levels irrespective of the size of radiation dose and time post irradiation. Renal protective factors calculated as the ratio of 80% survival times for animals fed the 20% protein diet compared to animals fed the 4% protein diet can be calculated to be 2.3 at 18 Gy and 2.8 at 22 Gy. Likewise, a SUN protective factor calculated as the ratio of percentage of nonirradiated control SUN values for the two diets (SUN 20% irradiated) (SUN 20% nonirradiated) (SUN 4% irradiated) (SUN 4% nonirradiated) is 2.4 for 18 Gy and 3.9 for 22 Gy.