Free radical mediated injuries after coronary artery occlusion

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Abstract
The left descending coronary artery (LAD) of mongrel dogs was ligated for one month to evaluate the effect of a dihydroquinoline-type antioxidant (MTDQ-DA) during the healing process of myocardial infarction. Thirty animals were divided into three groups: I) control animals (10 dogs) were treated with saline infusion during operation and postoperative days; II) 10 dogs were treated with intravenous MTDQ-DA during the operation followed by postoperative oral treatment, and III) 10 animals were treated with preoperative and postoperative oral treatment plus intraoperative MTDQ-DA infusion. The antioxidant effects were evaluated by measurements of the lipid peroxidation end product malondialdehyde (MDA) and of endogenous scavengers: reduced glutathione (GSH) and superoxide dismutase (SOD) in the ischemic and in intact areas. Ultrathin sections were investigated by JEOL 100 C electron microscope. Elevation of lipid peroxidation (LPO) was present in each group. The most remarkable changes were seen in the control ischemic areas (152±6.7%). GSH was depleted in the infarcted areas of the control hearts (60±5.6%), in the antioxidant treated animals this thiol compound was only slightly decreased (81±5.6%). SOD activity showed a sharp decline (group I) in both ischemic (52±8.3 U/g) and non-ischemic parts of the left ventricle (78±7 U/g). After MTDQ-DA treatment (groups II, III) SOD activity diminished only in the ischemic area (83±8.5 U/g); other parts showed normal (123±7.2 U/g) activity. According to ultrastructural examinations, MTDQ-DA diminished the degree of structural injury.