RENAL DENERVATION POTENTIATES THE NATRIURETIC AND DIURETIC EFFECTS OFATRIAL-NATRIURETIC-PEPTIDE IN ANESTHETIZED RABBITS

1. The role of the renal nerves in modulating the action of atrial nat riuretic peptide (ANP) in the kidney was studied by comparing the resp onses to ANP in innervated and surgically denervated kidneys in anaest hetized rabbits. 2. A low dose of ANP (0.05 mu g/kg per min, i.v.) was used to minimize the confounding effects of systemic hypotension. 3. The natriuretic and diuretic responses to ANP were significantly great er in denervated kidneys than in kidneys with intact innervation. Sodi um excretion from denervated kidneys rose by 7.49+/-3.11 mu mol/min in response to ANP (similar to 55%, P<0.05) compared to 0.84+/-0.59 mu m ol/min (similar to 28%, NS) in innervated kidneys. Urine flow increase d markedly in denervated kidneys by 73.2+/-29.9 mu mol/min (similar to 60%, P<0.05) but not in innervated kidneys. 4. Fractional sodium excr etion increased significantly in denervated kidneys in response to ANP (median 2.3% to median 3.0%, P<0.05). 5. Renal blood flow, glomerular filtration rate (GFR) and glomerular capillary pressure were unchange d in response to ANP in either denervated or innervated kidneys. Pre-g lomerular vascular resistance fell in denervated kidneys during ANP in fusion. 6. The natriuresis and diuresis observed in the denervated kid neys, due to an increased fractional excretion of sodium without incre ases in GFR or glomerular capillary pressure, is consistent with effec ts of ANP on tubular reabsorption of sodium. 7. Thus, ANP produced a n atriuresis and diuresis at a low dose in denervated but not in innerva ted kidneys. This indicates that reflex activation of renal nerves may antagonize the renal effects of ANP.