Lack of prejunctional modulation of noradrenaline release by endogenous nitric oxide in guinea pig pulmonary artery.

Abstract The regulation of noradrenaline (NA) release by endogenous endothelium-derived compounds was investigated in the isolated guinea pig pulmonary artery preloaded with [ 3 H ]NA. The radioactivity uptake, the basal and electrical field stimulation (10 Hz, 2 ms, 360 shocks) evoked release of [ 3 H ]NA was similar in arteries with intact endothelium and after removal of the endothelium. The wide selectivity nitric oxide (NO) synthase inhibitor N -ω-nitro- l -arginine (100 μM) did not affect significantly the basal and stimulation-evoked release of [ 3 H ]NA in control and endothelium-denuded preparations. These results indicate that neither endogenous NO nor other compounds derived from the endothelium have substantial influence on the NA outflow from sympathetic nerves innervating the pulmonary artery.