Role of atrial peptide in the acute natriuretic response to uninephrectomy

Unilateral nephrectomy (UNX) is associated with an immediate natriuretic response of the remaining kidney. The role of atrial natriuretic peptide (ANP), as assessed by right atrial appendectomy (APX), was investigated in euvolemic anaesthetized rats. In sham APX rats, UNX resulted in a twofold increase in urinary sodium and potassium excretion (1.03 +/- 0.11 to 2.08 +/- 0.17 and 1.39 +/- 0.05 to 2.26 +/- 0.08 mueq/min, respectively) and a doubling of urinary excretion of guanosine 3',5'-cyclic monophosphate (cGMP). No significant change in glomerular filtration rate, renal plasma flow, and lithium clearance occurred in response to UNX. APX totally prevented the UNX-induced natriuresis and diuresis as well as the rise in urinary cGMP. Post-UNX plasma concentration of ANP was higher in sham-operated compared with APX rats (45 +/- 9 vs. 20 +/- 2 fmol/ml). In sham APX rats, UNX was associated with a transient (less than 15 min) rise in arterial pressure; in APX rats, this immediate increase in arterial pressure was of similar magnitude but of longer (greater than 30 min) duration. The observed stimulation of ANP release after UNX and the blunting of the natriuretic response to UNX by APX suggest that ANP may be an important mediator of the renal response to contralateral renal ablation.