Dietary protein intake and the glomerular adaptations to partial nephrectomy in dogs

Brown, S. A.; Finco, D. R.; Crowell, W. A.; Navar, L. G.

After partial nephrectomy (Nx) in rats, a temporal pattern of progressively declining renal function often develops. This pattern has been attributed to the development of glomerular hyperfiltration, hypertension and hypertrophy in remnant nephrons. In rats, dietary protein restriction prevents these adaptive changes in remnant nephrons, thereby preserving renal structure and function. However, long-term studies of the temporal pattern of renal function have failed to identify a consistently progressive deterioration of renal function in partially Nx dogs, and a protective effect of protein restriction has not been apparent in this species. To address these issues in dogs, we evaluated the single nephron adaptations to partial Nx in dogs and the effect of dietary protein restriction on these adapatations. Results of our micropuncture studies in partially Nx dogs indicate that remnant nephrons of dogs exhibit glomerular hyperfiltration (single nephron glomerular filtration rate of 144 .+-. 8 vs. 71 .+-. 4 nL/min in controls, P < 0.05), hypertension (glomerular capillary pressure of 75.1 .+-. 1.6 vs. 63.2 .+-. 1.9 mm Hg in controls) and hypertrophy (glomerular volume of 3.54 .+-. 0.24 .times. 0.24 .times. 106 vs. 2.04 .+-. 0.05 .times. 106 .mu.m3 in controls, P < 0.05). Our studies of the effect of protein restriction on the adaptive changes of nephron structure and function after renal mass reduction in dogs indicate that moderate protein retriction did not prevent the development of glomerular hyperfiltration (single nephron glomerular filtration rate of 187 .+-. 15 vs. 62 .+-. 9 nL/min in controls, P < 0.05), hypertension (glomerular capillary pressure of 79.2 .+-. 3.2 vs. 59.3 .+-. 5.1 mm Hg in controls) and hypertrophy (glomerular volume of 4.84 .+-. 0.54 .times. 106 vs. 1.86 .+-. 0.25 .times. 106 .mu.m3 in controls, P < 0.05). These results demonstrate that glomerular hyperfiltration, hypertension and hypertrophy occur after partial Nx in dogs. However, effects of dietary intervention, specifically protein restriction, on these adaptations remain to be established.