Effect of time on remnant glomerular function.

Abstract

1. Although hypertrophy and hyperfiltration have been identified in remnant nephrons, the time of their appearance and the relationship between them have not been established. In order to evaluate remnant glomerular hemodynamics over different periods of time, we studied Munich-Wistar rats 7, 30 and 60 days after 5/6 renal mass ablation. 2. Kidney weight increased after 7 days, continued to increase after 30 days and decreased after 60 days. Glomerular filtration rate (GFR) and renal plasma flow decreased by 67% and 7 days, were 35% lower than normal after 30 days, and after 60 days presented the same values as after 7 days. Single-nephron GFR and glomerular plasma flow increased slightly after 7 days, were 118% higher than control after 30 days, and decreased after 60 days. Hydraulic glomerular capillary pressure tended to increase after 30 days (6%), reaching statistical significance after 60 days (45 vs 62 mmHg). The glomerular ultrafiltration coefficient increased significantly after 30 days (82%) and decreased to values similar to the control group after 60 days. 3. These data suggest that kidney hypertrophy occurs early after reduction of renal mass, before the hemodynamic adaptations are complete. Glomerular hypertension was observed after 60 days, when single-nephron GFR and the glomerular ultrafiltration coefficient were decreased compared to rats studied after 30 days. 4. These data may indicate that, once glomerular hypertension starts, structural abnormalities are followed by a decline in glomerular function.