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 protective 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-perfused with Krebs-Henseleit solution at 5 ml/min. After a 60-min equilibration, oxyradical challenge was instituted by the addition of H2O2 (200-600 microM) to the perfusate for 60 min. A subgroup of animals received DFX (400 microM) in the perfusate prior to challenge with 400 microM H2O2. Contractility was continuously monitored; perfusate samples for glutathione (GSH) and lactate dehydrogenase (LDH) estimations were collected at 30-min intervals. Headspace ethane, an indicator of lipid peroxidation, was estimated at 30-min intervals by gas chromatography. Control hearts maintained contractility during the perfusion period. H2O2 perfusion caused a dose dependent decrease in myocardial contractility; DFX pretreatment was partially protective. Headspace ethane slowly accumulated in control hearts; perfusion with H2O2 caused dose dependent increase in ethane accumulation indicative of enhanced lipid peroxidation. GSH and LDH in the perfusate remained low in control hearts. In contrast, H2O2 treated hearts had a dose dependent increase in the efflux of GSH and LDH which was markedly increased by perfusion with 600 microM H2O2. Pretreatment with DFX did not significantly reduce GSH or LDH efflux from hearts perfused with peroxide. While H2O2 perfusion causes a dose dependent decrease in myocardial contractility with a corresponding increase in headspace ethane release with GSH & LDH efflux indicative of oxidative stress, concurrent treatment with DFX reduces myocardial dysfunction and ethane generation. However, sublethal damage of plasma membrane still continues as reflected by continuous enhancement of LDH efflux, possibly indicating involvement of other reactive species besides hydroxyl radical.