Single-nephron adaptations to partial renal ablation in cats

To evaluate remnant nephron hyperfiltration, cats underwent sham surgery (group 1, n = 6) or three-fourths nephrectomy (group 2, n = 6). Four to six weeks later, micropuncture studies demonstrated increases (P < 0.01) of single-nephron glomerular filtration rate (SNGFR) in group 2 (28.1 +/- 2.8 vs. 56.0 +/- 5.9 nl/min). In group 2 the mean estimated glomerular capillary pressure of 74.0 +/- 1.7 mmHg exceeded (P < 0.01) the value for group 1 (62.6 +/- 1.4 mmHg). The mean effective filtration pressure (EFPm) for group 2 (28.7 +/- 3.1 mmHg) was greater (P < 0.05) than that in group 1 (20.8 +/- 1.9 mmHg). Similarly, the mean ultrafiltration coefficient (Kf) in group 2 of 2.03 +/- 0.24 nl.min-1.mmHg-1 exceeded (P < 0.05) the corresponding value for group 1 of 1.35 +/- 0.06 nl.min-1.mmHg-1. Morphological studies demonstrated glomerular enlargement and mesangial matrix expansion in group 2 (P < 0.05). Proteinuria, as assessed by the urine protein-to-creatinine ratio, was increased (P < 0.05) after partial renal ablation. These results demonstrate that increases in SNGFR in feline remnant nephrons occur in association with glomerular hypertension, glomerular hypertrophy, expansion of mesangial matrix, and proteinuria, and furthermore, that the observed increases in SNGFR are attributable to an augmentation of EFPm and Kf.