Ischemic preconditioning alters real-time measure of O₂ radicals in intact hearts with ischemia and reperfusion

Abstract

Reactive oxygen species (ROS) are believed to be involved in triggering cardiac ischemic preconditioning (IPC). Decreased formation of ROS on reperfusion after prolonged ischemia may in part underlie protection by IPC. In heart models, these contentions have been based either on the effect of ROS scavengers to abrogate IPC-induced preservation or on a measurement of oxidation products on reperfusion. Using spectrophotofluorometry at the left ventricular wall and the fluorescent probe dihydroethidium (DHE), we measured intracellular ROS superoxide (O(2)(-).) continuously in isolated guinea pig heart and tested the effect of IPC and the O(2)(-). scavenger manganese(III) tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP) on O(2)(-). formation throughout the phases of preconditioning (PC), 30-min ischemia and 60-min reperfusion (I/R). IPC was evidenced by improved contractile function and reduced infarction; MnTBAP abrogated these effects. Brief PC pulses increased O(2)(-). during the ischemic but not the reperfusion phase. O(2)(-). increased by 35% within 1 min of ischemia, increased further to 95% after 20 min of ischemia, and decreased slowly on reperfusion. In the IPC group, O(2)(-). was not elevated over 35% during index ischemia and was not increased at all on reperfusion; these effects were abrogated by MnTBAP. Our results directly demonstrate how intracellular ROS increase in intact hearts during IPC and I/R and clarify the role of ROS in triggering and mediating IPC.

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“…Vanden Hoek et al (109) and Damerau et al (28) also observed increased ROS production during hypoxia in cardiac myocytes. These data are consistent with earlier observations by Park et al (84) using electron spin resonance (ESR) in intact hearts during ischemia and Kevin et al (58) using redox sensitive fluorescent probes in the intact heart. Moreover, Duranteau et al (33) showed that the extent of increase in dichlorofluorescin fluorescence in cardiomyocytes was proportional to the severity of hypoxia.…”

Mitochondrial Uncoupling Protein 1 Expressed in the Heart of Transgenic Mice Protects Against Ischemic-Reperfusion Damage

“…18,19 Many of these ROS are of mitochondrial origin, and their production increases together with the reduction of components of the respiratory chain. 20,21 This can be a result of a high membrane potential that opposes proton pumping and therefore electron transfer by respiratory chain complexes.…”

Chemoreception in the context of the general biology of ROS

“…Nonetheless, there are some observations in our previous experiments (He et al, 2005) and in those of Kevin et al (2003) that do not fit the reliability concept, i.e., that dihydroethidium, upon its reaction with ROS (mostly O 2 •− ), generates fluorescent oxidized products which remain trapped inside the cells and therefore quantification of the fluorescence yields a measurement of the amount of ROS produced. In both of these studies it has been found that short pulses of sodium azide or full ischemia generated fluorescent signals that disappear on the elimination of the sodium azide or on restitution of the flow.…”