Functional evidence for renorenal reflexes in the rat

Acute left renal denervation in anesthetized volume-expanded rats produced an ipsilateral diuresis and natriuresis in 19 animals. A simultaneous decrease of glomerular filtration rate, p-aminohippurate clearance, urinary volume (P < 0.002), and percentage of filtered sodium excreted (4.0 +/- 0.6 (SE) vs. 1.9 +/- 0.4%, P < 0.003) occurred in the right innervated kidney in 10 rats. Prior denervation of the right kidney in the other nine rats prevented the renal hemodynamic changes and the fall of urinary volume and of sodium excretion (3.9 +/- 0.6 vs. 4.3 +/- 0.5%) by the right kidney after left renal denervation. Nerve traffic to the right kidney was measured in six other animals after left renal denervation and was found to increase to a mean value 33.8 +/- 6.3% above control levels (P < 0.007) 0-30 min after denervation, with a further significant increase to 66.2 +/- 16.1% above control levels (P < 0.025) 30-60 min after denervation. These results indicate that the functional changes in the right kidney after contralateral renal denervation in volume-expanded rats are caused by a reflex increase in nerve traffic to the right kidney, possibly as a consequence of an interruption of afferent nerve activity originating in the left kidney.