2-methyl-6-(4-methoxyphenyl)-3-7-dihydroimidazo(1-2-alpha)pyrazin-3-one and Disease-Models--Animal

To investigate the time course of superoxide generation in ischemia-reperfusion in the in-vivo rat lung, the present study used an enhanced chemiluminescence method with 2-methyl-6-[p-methoxyphenyl]-3,7-dihydroimidazo[1, 2-alpha]pyrazin-3-one (MCLA) as a specific probe. The right pulmonary artery was occluded for 120 min, followed by 90-min reperfusion. Chemiluminescence induced by MCLA was continuously monitored by a photomultiplier exposed to the right lung. Chemiluminescence increased gradually in 30 min of reperfusion and remained elevated throughout reperfusion. The ratio of the luminescence count during reperfusion to the preischemic value increased to 2.20+/-0.31 (mean+/-SEM) (p<0.02 vs preischemic level), 2.50+/-0.39 (p<0.005), and 2.69+/-0.44 (p<0.005), at 30, 60, and 90 min of reperfusion, respectively. Bolus administration of superoxide dismutase during the reperfusion period significantly attenuated the chemiluminescence by 45.0+/-6.7% (p<0.01). The present results suggest that increasing oxygen radical formation leading to ischemia-reperfusion lung injury may occur even after a short period of occlusion of the pulmonary artery alone in vivo.

Topics: Animals; Arterial Occlusive Diseases; Disease Models, Animal; Free Radical Scavengers; Imidazoles; Kinetics; Luminescent Measurements; Lung; Male; Pulmonary Artery; Pyrazines; Rats; Rats, Wistar; Reperfusion Injury; Superoxide Dismutase; Superoxides

Reocclusion following thrombolysis is a major limitation of thrombolytic therapy with recombinant tissue-type plasminogen activator (rt-PA) because denuded vessel wall exposed to blood following thrombolysis is a favourable surface for platelet and leucocyte deposition. We have applied a chemiluminescence technique to detect superoxide radical (0(-2)) produced by leucocytes adherent to the femoral artery 24 h after photochemically induced thrombogenesis in the guinea pig in vivo and subsequent thrombolysis by rt-PA. Intravenous administration of MCLA, a specific chemiluminescence reagent for detecting O(-2), markedly increased photon emission. the photon emission was markedly potentiated by phorbol myristate acetate and was suppressed by superoxide dismutase. Reocclusion 24 h after rt-PA induced thrombolysis was observed in 10 of 16 animals. Histological observations revealed extensive polymorphonuclear leucocytes adherent to the vessel wall at the site of thrombogenesis and thrombolysis. A higher level of 0(-2) could be detected from the arteries in which thrombolysis was induced compared with those without thrombolysis. Further, the level 0(-2) detected was greater in reoccluded arteries compared with those in which reflow was established. These observations suggest that 0(-2) is produced by adherent leucocytes at the site of thrombolysis and that leucocytes are involved in reocclusion after thrombolysis.

Topics: Animals; Cell Adhesion; Disease Models, Animal; Endothelium, Vascular; Femoral Artery; Guinea Pigs; Imidazoles; Light; Luminescent Measurements; Male; Neutrophils; Plasminogen Activators; Pyrazines; Recombinant Proteins; Rose Bengal; Superoxides; Thrombolytic Therapy; Thrombosis