Hydroxyl radical production during early reperfusion after different periods of ischemia in rat hearts and its effect on myocardial function

To elucidate the significance of hydroxyl radical (·OH) in postischemic reperfusion injury, we measured the ·OH production in the coronary effluent collected from isolated perfused rat hearts during reperfusion period of 15 minutes after various ischemic intervals ranging from 5 to 60 minutes. Salicylic acid was used as a probe for ·OH formation, and its derivative, 2,5-dihydroxybenzoic acid (2,5-DHBA), was quantified using high performance liquid chromatography. A significant amount of 2,5-DHBA was detected from the hearts rendered ischemic for 10 minutes and longer. The peak of 2,5-DHBA was seen within 90 seconds after the onset of reperfusion in every group, and the accumulated amount of 2,5-DHBA was maximal in 15 minutes ischemia group (3.97±0.49 nmol/g/15 minutes reperfusion) in contrast to 1.22±0.30 nmol/g/15 minute in 60 minutes ischemia. This study demonstrated an ischemic time-dependent ·OH production during reperfusion, and no direct effect of ·OH was observed on the post-ischemic injury related to myocardial function.