NO CONCENTRATION IN, THE PERIENDOTHELIAL AREA OF THE FEMORAL-ARTERY OF THE DOG MEASURED IN-VIVO

. NO concentration was measured in the periendothelial area of the fem oral artery by Malinski's porphyrinic . NO sensor in seven anaesthetiz ed dogs. The basal concentration was 154.2+/-5.6 nM and two-minute int raarterial infusions of acetylcholine (3-4 mu g/ml/min) or bradykinin (30-40 ng/ml/min) increased this value significantly to 204.3+/-16.4 a nd 266.5+/-16.4 nM (P<0.01), respectively. Inhibition of . NO synthase by L-NAME (50 mg/kg) declined the basal . NO concentration only to 13 7.2+/-3.3 nM (P<0.01). Subsequent administration of acetylcholine and bradykinin attenuated significantly the increase in . NO concentration . Surprisingly, both agonists still induced a significant increase of . NO concentration by 125.3+/-8.3 and 156.6+/-26.9 nM, respectively (P <0.01). One of the possible explanations may be that besides arginine- citrulline plus the . NO pathway other sources of . NO could be involv ed in the high level of . NO after . NO synthase blockade by L-NAME.