In order to clarify the time course of
superoxide generation in situ during
ischemia and reperfusion in the rabbit heart, we used a method of enhanced chemiluminescence (CL) with 2-methyl-6-[p-methoxyphenyl]-3, 7-dihydroimidazo [1, 2-alpha]pyrazin-3-one (
MCLA) as a specific probe for detecting
superoxide radicals. The surface of the rabbit heart was exposed to a photomultiplier tube in a light-proof box. We introduced a reversible snare occluder into the box to continuously observe the light emission. An
ischemia-reperfusion group (I/R, n = 7) was subjected to 30 mins of
coronary occlusion, followed by 90 mins of reperfusion. We performed the same procedure (except for
coronary occlusion) in the
sham-operated group (n = 4). Another group of rabbits (n = 4) subjected to I/R received
superoxide dismutase (SOD: 20 mg/kg, i.v.) during reperfusion to observe the CL response. In the I/R-group, the increase in CL began at 13 +/- 2 (mean +/- SEM) mins and peaked at 52 +/- 12 mins of reperfusion. CL in the I/R-group gradually increased from 818 +/- 350 counts/10 secs in the preischemic period to 1077 +/- 401 counts/10 secs during reperfusion (p < 0.01). In contrast, there was no increase in CL in the
sham-operated group. The administration of SOD briefly attenuated CL by 24.1 +/- 6.8% for a period of 24.3 +/- 6.8 mins. The
superoxide generation in situ in the ischemic rabbit heart appears to increase gradually and persists for a period following reperfusion.