The Mechanism of Denervation Natriuresis *

Abstract

The mechanism by which acute denervation of the kidney increases sodium excretion has been studied by comparison of denervated and intact kidneys in each of 13 saline loaded dogs. Following the collection of pre-denervation periods, the left greater splanchnic nerve was sectioned and a set of "denervation" periods was obtained. A clamp around the left renal artery was then tightened until the sodium excretion ratio, experimental over control kidney, has been returned to its predenervation value. After denervation the mean sodium excretion ratio rose to 1.66, a value significantly different from the mean pre-denervation value of 1.06. The mean GFR [glomerular filtration rate] ratio also increased significantly from 1.03 to 1.13. During the "clamp" periods the mean sodium excretion ratio was returned to 1.05, a value not significantly different from the mean pre-denervation ratio of 1.06. With the sodium excretion thus returned to pre-denervation values, the mean clamp GFR ratio was found to be 1.00, a value not significantly different from the mean pre-denervation ratio of 1.03. The disappearance of the denervation natriuresis when filtered sodium was retured to predenervation values by clamping is evidence against a direct effect of renal nerves on tubular sodium reabsorption and indicates that acute denervation natriuresis results solely from increased GFR.