Renal denervation in the rat: analysis of glomerular and proximal tubular function

We examined 1) the potential modifications in both single nephron filtration rate (SNGFR) and the determinants of glomerular ultrafiltration, and 2) the alterations in peritubular capillary (PTC) "physical factors" that may contribute to changes in proximal tubular reabsorption (APR) after acute renal denervation (DNx). Micropuncture measurements were obtained in euvolemic Munich-Wistar rats with DNx or sham operation (sham). The content of norepinephrine in renal tissue homogenates was markedly reduced in DNx kidneys compared with sham kidneys (P less than 0.001). Mean arterial blood pressure, hematocrit, whole kidney GFR, and urinary flow rate were not different between the sham and DNx groups. Absolute urinary sodium excretion was 3 times greater in the DNx than in the sham group (P less than 0.01). SNGFR and its determinants were not statistically different in the two experimental conditions. APR was significantly reduced by approximately 25% in DNx (P less than 0.02). This reduction in APR was not accompanied by significant directional changes in peritubular capillary and renal interstitial pressures and the passive driving forces acting across the PTC-proximal tubular epithelium. These data demonstrate that elimination of renal innervation does not alter SNGFR or its determinants and suggest that the effect of denervation on APR is a primary epithelial event that occurs independent of changes in renal interstitial pressure and peritubular oncotic and hydrostatic pressures.