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

Abstract

The effect of bilateral renal denervation on Na excretion was studied in conscious rats on normal, low and high Na diet, and in rats recovering from anesthesia, as well as in anesthetized rats fed a normal Na diet. Na excretion of bilaterally denervated conscious rats on normal Na intake and during either 2 wk of Na depletion or 6 days of Na loading was not different from that of controls, despite changes in Na supply of more than 2 orders of magnitude. Cortical noradrenaline [norepinephrine] concentration of control kidneys was 138 .+-. 12 ng/g, but was only 7 .+-. 3 ng/g (P < 0.001) 6 wk after denervation. In rats recovering from anesthesia urine flow, Na excretion and glomerular filtration rate (GFR) were not affected by denervation. In anesthetized nondiuretic rats on normal Na diet, chronic bilateral renal denervation increased urine flow and Na excretion by 4 and 5 times, respectively with no changes in GFR. Mean arterial blood pressure in bilaterally denervated anesthetized rats and in those recovering from anesthesia was decreased by 2.7 kPa [kilopascal], P < 0.001, and 1.2 kPa, P < 0.05, respectively. The participation of renal nerves in the regulation of Na excretion in conscious rats seems improbable. The denervation natriuresis in anesthetized rats can be related to higher predenervation renal sympathetic nervous activity due to narcosis and surgical stress.