RENAL VASOCONSTRICTION IS MODULATED BY NITRIC-OXIDE

1. The effect of the nitric oxide synthesis inhibitor, N(G)-nitro-L-arginine (NOLA), has been examined on vascular reactivity in the rat isolated perfused kidney. 2. NOLA(10-mu-mol/L) had no effect on basal perfusion pressure, but significantly enhanced the vasoconstrictor responses to sympathetic nerve stimulation (1-16 Hz, 10 s) and noradrenaline (10-300 pmol). The enhancements were greater with the lower frequencies of stimulation and lower doses of noradrenaline. 3. The enhancing effect of 10-mu-mol/L NOLA on vasoconstrictor responses to nerve stimulation was partially prevented by 100-mu-mol/L L-arginine while 100-mu-mol/L D-arginine had no effect. 4. The results suggest that nitric oxide attenuates vasoconstrictor responses in the rat kidney, and provide evidence that nitric oxide has a physiological role in the modulation of vascular reactivity.