ANTAGONIZING THE HYDROXYL ION FREE-RADICAL (HO.) DOES NOT ABOLISH REPERFUSION VENTRICULAR-FIBRILLATION IN ANESTHETIZED DOGS

1. The hypothesis that the hydroxyl ion free radical, HO., derived fro m O2 plays a pivotal role in the development of reperfusion ventricula r fibrillation was tested in 63 anesthetized mongrel dogs of either se x weighing 14 +/- 7 kg submitted to 90-min coronary occlusion followed by 60-min reperfusion. 2. OH. was blocked by the iron chelator defero xamine (DF,500 mg) and by dimethylthiourea (DMTU, 500 mg/kg), a HO. sc avenger both given iv over 30 min before reperfusion. 3. The frequency of reperfusion ventricular fibrillation was similar in all animals, i .e., 7/27 (26%) control dogs, 7/23 (30%) DF-treated dogs and 3/13 (23 %) DMTU-treated dogs. Arterial pressure, heart rate and double product were not significantly different among the three groups during occlus ion or reperfusion. The hemodynamic variables were also similar among dogs that fibrillated and those that did not. Likewise, extent of isch emic areas and necrosis was similar among the three experimental group s, with the control values being 34 +/- 4% and 14 +/- 5%, respectively . 4. We conclude that OH. does not play a major role in the induction of reperfusion ventricular fibrillation in the anesthetized dog with i schemia/necrosis.