We studied 12
pentobarbital-anesthetized dogs 8 to 21 days after surgical placement of a femoral AV
fistula in order to characterize the renal response to subsequent closure and reopening of the
fistula. Closure of the
fistula resulted in a significant reduction in cardiac output from 3.3 +/- 0.2 L/min to 2.2 +/- 0.1 (p less than 0.001) and heart rate from 163 +/- 7 beats/min to 150 +/- 7 (p less than 0.005), whereas blood pressure did not change significantly. These changes in systemic hemodynamics were associated with significant increases in GFR, renal vascular resistance, and filtration fraction and a significant decrease in RBF. UNaV (16.4 +/- 3.8 microEq/min to 31.3 +/- 6.5), UKV (27.9 +/- 1.6 microEq/min to 47.5 +/- 3.8), and UHCO3V (6.8 +/- 1.4 mumol/min to 25.0 +/- 2.4) increased significantly (p less than 0.005), whereas UCIV was unchanged. Renal
denervation blunted the renal hemodynamic and natriuretic consequences of
fistula closure, but other
electrolyte excretory responses paralleled those in innervated kidneys. In innervated kidneys RSR fell significantly after
fistula closure; RSR was low in denervated kidneys and did not change on
fistula closure. Reopening the AV
fistula restored systemic hemodynamics toward initial control values but produced no further changes in renal hemodynamics or
electrolyte excretion. Overall, an inverse relationship between changes in
cation excretion and changes in RSR was observed in innervated kidneys. These results demonstrate involvement of the renal nerves as well as an increase in GFR in the increased
cation excretion that occurs after AV
fistula closure. However, persistently elevated
cation excretion after the reopening of the
fistula may be due to other mechanisms.