Renal handling of sodium after chronic renal sympathectomy in the anesthetized rat

Abstract

The effects of chronic renal sympathectomy (renal denervation) on whole kidney and single nephron function were evaluated in Inactin-anesthetized non-diuretic rats. Micropuncture experiments were performed in control, sham-denervated and unilaterally denervated animals. In 2 separate groups of denervated rats renal cortical blood flow and cortical norephinephrine concentration were determined as well. Unilateral chronic denervation resulted in a markedly higher Na and water excretion but with no change in either GFR [glomerular filtration rate] or cortical blood flow. Tissue norepinephrine concentration in denervated organs was negligible. As compared to controls (C), in denervated (D) kidneys both late proximal and early distal (TF/P)In ratios were significantly lower [proximal: C = 2.57 .+-. 0.05 (SE), D = 1.73 .+-. 0.04 (SE); distal: C = 6.27 .+-. 0.06 (SE), D = 3.97 .+-. 0.05 (SE)], with no difference in single nephron filtration. Proximal and distal (TF/P)urea ratios were also lower, but distal (Tf/P)Na and (TF/P)K ratios were higher in the chronically denervated kidneys. Proximal fractional reabsorption of Na, water and urea, and absolute reabsorption of Na and water were considerably depressed in the denervated group, while reabsorption of Na in more distal segments was higher than in control or sham-denervated rats. Chronic renal sympathectomy results in a primary decrease of proximal tubular reabsorption of filtrate with a partial compensation in distal parts of the nephron in the absence of hemodynamic changes. A direct action of chronic denervation on tubular transport of N2 can be suggested.