Effects of dietary protein on glomerular mesangial area and basement membrane thickness in aged uninephrectomized dogs

The primary objective of this study was to determine the effects of diets c ontaining 18% or 34% protein on glomerular mesangial area (GMA) and basemen t membrane thickness (GBMT) in uninephrectomized aged dogs. A secondary obj ective was to determine the combined effects of aging and uninephrectomy on GMA and GBMT in dogs. Ten clinically healthy, purebred dogs were unilatera lly nephrectomized at about 8 y of age. After 2 mo, 5 dogs were fed an 18% protein diet and 5 dogs were fed a 34% protein diet for 48 mo. At month 48, the dogs were euthanized and the remaining kidney was collected. Samples o f kidney from both times of collection were used to measure GMA and GBMT us ing electron microscopy. The effects of diet on GMA and GBMT were analyzed (student's t-test) using necropsy/nephrectomy score ratios. The effects of time-nephrectomy were determined by comparing nephrectomy values for GMA an d GBMT with necropsy values (paired t-test). Dogs fed 34% dietary protein d id not have a significant increase in GMA and GEM thickness when compared t o dogs fed the 18% protein diet. A significant increase in GMA and GBMT occ urred with time-nephrectomy (P = 0.011 and 0.018, respectively). Although d ietary protein intake was not a significant factor in causing structural ch anges to glomeruli in uninephrectomized aged dogs, the power to detect a di fference was low. However, significant effects of aging and nephrectomy wer e detected despite the low power of the study. These results suggest that t he increases in GMA and GBMT that occur over time are not markedly influenc ed by dietary protein intake. However, subtle protein effects cannot be eli minated as a possibility based on this study.