Effects of NG-Monomethyl-L-Arginine and L-Arginine on Acetylcholine Renal Response

Intrarenal infusion of acetylcholine in meclofenamate-treated dogs significantly increased renal blood flow, diuresis, and natriuresis. Intrarenal infusions of either N-monomethyl- L-arginine (inhibitor of endothelium-derived relaxing factor formation), or L-arginine (precursor of endothelium-derived relaxing factor formation) did not modify basal levels of those parameters. However, the infusion of N-monomethyl-L-arginine inhibited the acetylcholineinduced increases in renal blood flow and diuresis without affecting natriuresis, which increased significantly. The infusion of L-arginine failed to further enhance hemodynamic and excretory effects elicited by acetylcholine. The concomitant infusion of L-arginine and N°- monomethyl-L-arginine did not change renal blood flow, urine flow, or sodium excretion rate. L-Arginine administration prevented the inhibitory effect of N-monomethyl-L-arginine on acetylcholine-induced renal vasodilatation and diuresis. Glomerular filtration rate and mean arterial pressure did not change throughout the experiment The results indicate that the vasodilatory and diuretic responses to intrarenal acetylcholine in meclofenamate-treated dogs are largely dependent on endothelium-derived relaxing factor.