EFFECTS OF DEFEROXAMINE ON H2O2-INDUCED OXIDATIVE STRESS IN ISOLATED RAT-HEART

During myocardial reperfusion injury, iron has been implicated in the Fenton based generation of hydroxyl radical, . OH, leading to further organ injury. Although previous studies have investigated the protecti ve effect of iron chelators including deferoxamine (DFX) in myocardial reperfusion injury, there is little information regarding the role of iron chelation during oxidative stress produced by H2O2 on the heart. Isolated hearts from male Sprague-Dawley rats were retrograde-perfuse d with Krebs-Henseleit solution at 5 ml/min. After a 60-min equilibrat ion, oxyradical challenge was instituted by the addition of H2O2 (200- 600 mu M) to the perfusate for 60 min. A subgroup of animals received DFX (400 mu M) in the perfusate prior to challenge with 400 mu M H2O2 Contractility was continuously monitored; perfusate samples for glutat hione (GSH) and lactate dehydrogenase (LDH) estimations were collected at 30-min intervals. Headspace ethane, an indicator of lipid peroxida tion, was estimated at 30-min intervals by gas chromatography. Control hearts maintained contractility during the perfusion period. H2O2 per fusion caused a dose dependent decrease in myocardial contractility; D FX pretreatment was partially protective. Headspace ethane slowly accu mulated in control hearts; perfusion with H2O2 caused dose dependent i ncrease in ethane accumulation indicative of enhanced lipid peroxidati on. GSH and LDH in the perfusate remained low in control hearts. In co ntrast, H2O2 treated hearts had a dose dependent increase in the efflu x of GSH and LDH which was markedly increased by perfusion with 600 mu M H2O2. Pretreatment with DFX did not significantly re duce GSH or LD H efflux from hearts perfused with peroxide. While H2O2 perfusion caus es a dose dependent decrease in myocardial contractility with a corres ponding increase in headspace ethane release with GSH & LDH efflux ind icative of oxidative stress, concurrent treatment with DFX reduces myo cardial dysfunction and ethane generation. However, sublethal damage o f plasma membrane still continues as reflected by continuous enhanceme nt of LDH efflux, possibly indicating involvement of other reactive sp ecies besides hydroxyl radical.