Renal excretion of sodium after bilateral renal sympathectomy in the anaesthetized and conscious rat

Abstract

1. The effect of bilateral renal denervation on sodium excretion was studied in conscious rats on normal, low and high sodium diet, and in rats recovering from anaesthesia, as well as in anaesthetized rats fed a normal sodium diet. 2. Sodium excretion of bilaterally denervated conscious rats on normal sodium intake and during either 2 weeks of sodium depletion or 6 days of sodium loading was not different from that of controls, despite changes in sodium supply of more than two orders of magnitude. Cortical noradrenaline concentration of control kidneys was 138 +/- 12 ng/g, but was only 7 +/- 3 ng/g (P less than 0 . 001) 6 weeks after denervation. 3. In rats recovering from anaesthesia urine flow, sodium excretion and glomerular filtration rate (G.F.R.) were not affected by denervation. 4. In anaesthetized non-diuretic rats on normal sodium diet chronic bilateral renal denervation increased urine flow and sodium excretion four and five times, respectively, with no changes in G.F.R. 5. Mean arterial blood pressure in bilaterally denervated anaesthetized rats and in those recovering from anaesthesia was decreased by 2 . 7 kPa, P less than 0 . 001 and 1 . 2 kPa, P less than 0 . 05, respectively. 6. The participation of renal nerves in the regulation of sodium excretion in conscious rats seems improbable. The denervation natriuresis in anaesthetized rats can be related to higher pre-denervation renal sympathetic nervous activity due to narcosis and surgical stress.