EFFECT OF THE NO SCAVENGER CARBOXY-PTIO ON ENDOTHELIUM-DEPENDENT VASORELAXATION OF VARIOUS BLOOD-VESSELS FROM RABBITS

In the present study, we investigated the effect of a nitric oxide (NO ) scavenger, carboxyphenyl)-4,4,5,5-tetramethylimidazoline-oxyl 3-oxid e [carboxy-PTIO], on endothelium-dependent relaxation of a series of b lood vessels from rabbits, such as thoracic aorta and femoral, renal, mesenteric, and pulmonary arteries, using a functional muscle bath tec hnique. Carboxy-PTIO produced concentration-dependent contractions in various vessels. The contractile responses in renal, mesenteric, and p ulmonary arteries were significantly greater than those in the aorta a nd femoral artery. Similarly, phenylephrine-induced contractions in re nal, mesenteric, and pulmonary arteries were markedly enhanced after p retreatment with carboxy-PTIO. Also, carboxy-PTIO inhibited acetylchol ine-induced relaxation in various blood vessels. The maximum inhibitio ns in aorta and femoral artery were significantly greater than those i n renal, mesenteric, and pulmonary arteries. The present data demonstr ate that carboxy-PTIO reduces basal, phenylephrine-, and acetylcholine -induced release of NO in rabbit blood vessels. However, different deg rees of inhibition of endothelium-dependent vasorelaxation were observ ed in various vessels. Specifically, the thoracic aorta and femoral ar tery are less susceptible to the action of carboxy-PTIO without acetyl choline than renal, mesenteric, and pulmonary arteries. Conversely, th e most potent carboxy-PTIO-induced inhibition of acetylcholine-induced vasorelaxation was observed with aorta and femoral arteries. Thus, it is suggested that the contribution of endogenous NO to vascular tone and regional blood flow may vary among different rabbit blood vessels.