Proximal tubular transport and urinary excretion of sodium after renal denervation in sodium depleted rats

Abstract

The effect of unilateral renal denervation on renal handling of water, sodium and potassium was studied with clearance and micropuncture techniques in sodium depleted anaesthetized rats in the nondiuretic state. In clearance experiments renal denervation resulted in a +140 and +320% increase in urine flow and potassium excretion, but sodium excretion of innervated (I) and denervated (D) kidneys was similar (I: 12.0±2.0, D: 14.0±3.6 nM·min⁻¹·g⁻¹; NS). However, upon the loop diuretic furosemide (1 mg·kg⁻¹), a marked denervation natriuresis was observed (I: 2.8±0.9, D: 5.9±1.0 μM·min⁻¹;P<0.05) and denervation diuresis and kaliuresis persisted, too (+95 and +60%, respectively). Micropuncture results revealed that fractional reabsorption of filtrate to late proximal puncture site was depressed by renal denervation from 62 to 49% while no change in time control rats was seen (64±2 vs. 64±1%; NS). In micropuncture experiments besides augmented urine flow (+82%) from D kidneys also a small denervation natriuresis was present (I: 21.6±6.4, D: 29.2±7.0 nM·min⁻¹;P<0.05). It is concluded that the lack or marked attenuation of denervation natriuresis in sodium depleted rats were the result of an almost complete compensatory distal reabsorption of the excess sodium (but not of water and potassium) leaving the proximal tubule after denervation. The distal adaptive response can be overcome by furosemide.