Journal
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY
Volume 443, Issue 5-6, Pages 908-916Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s00424-001-0744-2
Keywords
reperfusion; mitochondria; respiration; bioenergetics
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This study examined whether different durations of ischaemia (I) and reperfusion (R) altered the kinetics of O-2 consumption-to-demand matching and the contribution of changes in calcium and metabolic pathways to possible alterations. The response time of mitochondrial O-2 consumption (t(mito)) to a step in heart rate in isolated rat hearts was used as index for the response time of O-2 consumption-to-demand matching. At baseline, t(mito) was 8.9+/-0.4 s for all groups. At 5 min reperfusion, after both reversible (I=5 or I=15 min) or irreversible (I=25 min) ischaemia, matching was accelerated (t(mito) relative to baseline: 53+/-8%. 64+/-8%, 51+/-6% and 100+/-5% for I=5, 15, 25 min and control). At late reperfusion (>30 min), reversible ischaemia resulted in a slowing of the matching, whereas after irreversible ischaemia t(mito) recovered to control values (156+/-16%. 153+/-13%. 92+/-7%. 114+/-6%, for I=5,15, 25 min and control., respectively). High perfusate Ca2+ mimicked (t(mito): 44+/-11%), whereas blocking mitochondrial Ca2+ uptake attenuated the acceleration observed at early reperfusion (t(mito): 74+/-5%). Replacing glucose with substrates used downstream of glycolysis (11 mM lactate or 11 mM pyruvate) abolished the reversible ischaemia-induced slowing of the matching at late reperfusion. It is concluded that I/R-induced changes in the kinetics of O-2 consumption-to demand matching depend critically on the duration of ischaemia and reperfusion. The data indicate that I/R-induced increases in Ca2+ may, at least partly, explain the faster kinetics at early reperfusion, whereas UR-induced increases in glycolysis from exogenous glucose result in slower matching of O-2 consumption-to-demand at late reperfusion.
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