2-methyl-6-(4-methoxyphenyl)-3-7-dihydroimidazo(1-2-alpha)pyrazin-3-one and Reperfusion-Injury

Abstract. The exact time profile of superoxide generation during anoxia-reoxygenation and ischemia-reperfusion was assessed in the feline cerebral cortex in vivo using a chemiluminescence technique with a probe specific for superoxide, 2-methyl-6-[p-methoxyphenyl]-3,7-dihydroimidazo[1,2-alpha]pyrazin-3-one (MCLA). MCLA solution was superfused on the cortex throughout the protocol, and MCLA chemiluminescence was measured using a newly developed photon counting system. Reflectance at 398 nm was simultaneously measured to compensate for hemodynamic artifacts resulting from cerebral blood volume changes. In 19 animals, a 90-second anoxia was induced by the inhalation of 100% nitrogen followed by a 40-minute reoxygenation. The chemiluminescence decreased during the period of anoxia (p < 0.01) and then exceeded the baseline level at 15 and 20 minutes after reoxygenation (p < 0.05). In six animals, superoxide dismutase (SOD) was continuously superfused and anoxia-reoxygenation was performed in the same manner. The chemiluminescence decreased during the period of anoxia (p < 0.05) but did not exceed the baseline level during the reoxygenation period, indicating that an increase in superoxide production was the main cause of the chemiluminescence increase. In eight animals, a 15-minute forebrain ischemia was induced by the occlusion of the bilateral common carotid arteries with systemic hypotension (systolic blood pressure less than 50 mmHg) followed by a 30-minute reperfusion. The chemiluminescence decreased during the period of ischemia (p < 0.01) and then increased at 20 and 25 minutes after reperfusion (p < 0.05). These results indicate that superoxide generation decreases during anoxia and ischemia and then increases within 20 minutes after reoxygenation or reperfusion.

Topics: Animals; Cats; Cerebral Cortex; Hemodynamics; Imidazoles; Luminescent Measurements; Oxygen; Photons; Pyrazines; Reperfusion Injury; Superoxides; Time Factors

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