Influence of renal denervation on urine concentration in awake and anaesthetized dogs

The role of renal nerves in urine concentration was studied in clearance experiments with unilaterally renal-denervated dogs prepared by surgical bladder division. Urine concentration was assessed under conditions of: (1) stimulation of ADH release by dehydration or barbiturate anaesthesia; (2) mannitol diuresis, and (3) isotonic saline diuresis. Differences in TcH2O/GFR between the intact and denervated kidney were not significant in any of the experimental groups. However, in dehydrated conscious dogs Uosm of the intact kidney (939 +/- 58 mmol/kg H2O) was significantly higher (P less than 0.05) than that of the denervated organ (806 +/- 51 mmol/kg H2O). In the intact kidney the medullary content of total solutes and sodium per kg wet tissue was 684 +/- 26 mmol and 208 +/- 12 mmol, respectively. This was significantly higher (P less than 0.005) than corresponding values of 581 +/- 23 mmol and 171 +/- 14 mmol per kg wet tissue measured in the denervated organ. We suggest that a slight impairment of urine concentration (lower Uosm) in the denervated kidney of conscious dogs may depend on decreased medullary hypertonicity.