Change of tubular reabsorption of sodium and water after renal denervation in the dog.

1. Renal function was compared in dogs before and after denervation, with normal or reduced glomerular filtration rate (GFR). GFR was reduced by one of two means, aortic clamping or injection of plastic microspheres into one renal artery.2. The data showed that the tubular rejection fraction of denervated kidneys increased at a time when the same value for the control kidney decreased, indicating that denervation diuresis is not simply a result of increased filtered load of Na and water.3. Changes in excretion after aortic clamping are not due solely to reduced filtered load. A reduction in renal blood pressure itself appears to have a direct effect on Na transport since Na excretion was significantly decreased before there were any changes in GFR, renal plasma flow and urine volume.4. When GFR in a denervated kidney was reduced by microsphere injection it was demonstrated that a significant natriuresis (U(Na) V) and diuresis (V) occurred when. GFR was reduced by as much as 40%.5. These experiments support the hypothesis that denervation diuresis does not result solely from increased filtered load, but entails altered Na transport.