SaO047
EFFECTS OF RENAL DENERVATION ON RENAL FUNCTION, PLASMA RENIN ACTIVITY AND BLOOD PRESSURE IN RATS FED A LOW POTASSIUM DIET Free

INTRODUCTION: Renal sympathectomy is successfully applied to improve blood pressure control in patients with treatment-resistant hypertension. The renal nerves effectively increase tubular transport of several ions, so it can be supposed that the denervated kidney cannot maintain homeostasis in case of mineral deficiencies. Therefore, we studied the effects of renal denervation on daily potassium excretion in potassium depleted rats, and also measured activity of the renin-angiotensin-aldosterone system (RAS) and blood pressure.

METHODS: Male Wistar rats were fed a control (NP) or potassium deficient (LP) diet (K+: NP=179, LP=13 mM/kg) for 7 days. Urinary sodium and potassium excretion was measured before and after acute left renal denervation (RD) in anesthetized (Inactin, 100 mg/kg, i.p.) rats (n=10/group). Blood pressure (BP) was recorded in the conscious state in acutely cannulated rats. Blood was taken for measuring plasma electrolytes, plasma renin activity (PRA) and aldosterone concentration. In a second series of experiments daily sodium and potassium excretion of rats with chronic bilateral renal denervation (BRD) or sham operation (SO) was measured in metabolism cages (n=11/group).

RESULTS: LP decreased plasma potassium concentration (NP=4.4±0.3, LP=3.0±0.1 mmol/L; p<0.05) and resulted in a compensated metabolic alkalosis. Acute RD increased urine flow (91±16%) sodium (289±54%) and potassium excretion (76±14%; p<0.05 for all) but GFR remained unchanged in rats on LP diet for 7 days. In the chronic experiment BP was lower (SO=102.8±2.9, BRD=93.5±2.3 mmHg; p<0.05), PRA (SO=13.5±1.9, BRD=6.8±1.3 ng/ml/h; p<0.05), and plasma aldosterone concentration (SO=12.7±1.2, BRD=9.4±0.5 ng/dl; p<0.05) decreased in rats with BRD compared to SO. On the first 6 days of potassium depletion daily potassium excretion progressively and similarly dropped in SO and BRD rats and then reached equilibrium. During the steady state period potassium excretion of BRD rats was 19-27 % higher (p<0.05) than those of SO rats.

CONCLUSIONS: Chronic bilateral renal denervation decreased normal blood pressure in rats at least in part due to decreased plasma renin activity. Renal denervation worsened potassium conservation capacity of the kidney, which might have clinical relevance.

Grant: NKFI-113164