Evidence for cholinergic innervation in dog renal tissue.

Abstract

Denervation procedures that affect the sympathetic system of the kidney, as demonstrated by norepinephrine depletion of renal tissue, increased urine volume, fractional sodium excretion, and free water clearance in anesthetized water-loaded dogs. These increases were reduced by atropine, which also blocked the increase above those basal functional levels produced by acetylcholine in both innervated and denervated kidneys. An in vitro tubular cell preparation of innervated kidneys corresponding to the outer cortex showed [3H]quinuclidinyl benzilate (QNB) binding parameters characteristic of muscarinic receptors. Denervation did not change either [3H]QNB binding parameters or the ability of inner and outer cortex cells to perform the hemicholinium-3-inhibitable, sodium-dependent choline uptake and conversion of [3H]choline to [3H]acetylcholine. This cell membrane behavior is similar to that observed in tissues where cholinergic neuronal structures are present, suggesting the existence of a cholinergic innervation of the kidney, independent of the integrity of vessel-traveling nerves. Similarly, the finding of choline acetyltransferase in renal tissue, unaffected by sympathetic denervation, seems to confirm the presence of cholinergic nerve terminals. The cholinergic system may thus contribute to the regulation of tubular reabsorption of sodium and water in some conditions.