Renal nerve blunts natriuretic and diuretic response to atrial natriuretic peptide in conscious rabbits

The contribution of the renal nerve to the natriuretic and diuretic responses to rat atrial natriuretic peptide (rAMP) was investigated in conscious rabbits with unilateral renal denervation. Renal nerve activity (RNA) was measured at the contralateral innervated kidney. Catheters were bilaterally implanted into the ureters. Urine samples were collected from each kidney by gravity drainage at 10-min clearance intervals. In rabbits with all baroreflexes intact, infusion of rANP at 0.3 micrograms/(kg.min) for 30 min decreased mean arterial pressure by 8 +/- 4 mmHg and increased RNA by 53 +/- 13%. After sinoaortic baroreceptor denervation (SAD), hypotensive response to infusion of rANP was greater than that in intact rabbits, while RNA did not change. After SAD plus vagotomy, infusion of rANP lowered mean arterial pressure by 21 +/- 4 mmHg and RNA by 19 +/- 6%. In the denervated kidney, infusion of rANP increased Na+ excretion by 16.1 +/- 4.5 from 3.5 +/- 1.0 muEq/min and water excretion by 0.17 +/- 0.05 from 0.08 +/- 0.02 ml/min. In the contralateral innervated kidney, infusion of rANP increased the amount of Na+ and water excretion by 4.5 +/- 3.2 muEq/min and 0.07 +/- 0.04 ml/min, which were significantly less than those in the denervated kidney. These results indicate that infusion of rANP increases RNA, due to baroreceptor reflexes, and that this increase in RNA blunts natriuretic and diuretic action of rANP.