Renal sodium handling in intact and renal denervated dogs

The ability to retain sodium was investigated in six conscious dogs before and after surgical renal denervation. Dietary sodium and water intake were kept constant (2.5 mmol Na X kg-1 bw X day-1 and 91 ml water X kg-1 bw X day-1). Balance experiments were performed from 6 days before to 8 days after having produced a sodium deficit of 6.4 +/- 0.4 (intact dogs) and 5.8 +/- 0.2 (renal denervated dogs) mmol Na X kg-1 bw by means of a peritoneal dialysis (PD). Having the same sodium excretion before PD, intact and renal denervated dogs demonstrated a similar striking decrease of sodium excretion and a similar increase of plasma renin activity after PD until the amount of sodium lost had been replenished (4th day after PD). In intact and renal denervated dogs plasma sodium concentration (PNa) decreased and renal water excretion increased on the first day after PD, indicating a homeostatic response to the fall of PNa. After dietary sodium restriction (from 2.5 to 0.5 mmol Na X kg-1 bw X day-1) a similar striking decrease of renal sodium excretion occurred in intact and renal denervated dogs. It therefore is concluded that in conscious dogs the presence of the renal nerves is not essential in order to maintain body sodium homeostasis after an acute sodium loss or after dietary sodium restriction.