Abstract 340: Marked Attenuation of Cell Injury by Substrate Availability During Ischemia
Background: Ischemic injury in cardiomyocytes results in rigor contracture (reduction of length by approximately one third) and reperfusion injury results in hypercontracture (change of morphology from rod-shaped to round forms). Rapid reoxygenation during reperfusion at high oxygen concentrations during limited substrate availability could augment cell injury. We therefore hypothesized that substrate availability during ischemia delays rigor and delayed and gradual reoxygenation reduces hypercontracture. Then, we compared the effects of normocarbic immediate (NIR) and hypercarbic delayed reoxygenation (HDR) following aglycemic anoxia (AA) and normoglycemic anoxia (NA) in isolated adult rat cardiomyocytes.
Methods: The set-up for creating anoxic environment incorporated (i) a gas blender, (ii) equilibration of ischemic buffer with anoxic gas mixture and perfusing the chamber, and (iii) an acrylic hood, constantly flushed with anoxic gas mixture, to cover the chamber on the stage of the microscope. This set-up resulted in PO2 of 0 mmHg constantly over a period of time. The cells were subjected to 15 min of baseline, 45 min of simulated ischemia and 120 min of simulated reoxygenation (AA-NIR, NA-NIR, AA-HDR, and NA-HDR) with or without glucose as a substrate.
Results: Substrate availability significantly reduced the occurrence of rigor and hypercontracture (AA vs NA followed by any reoxygenation protocol: p<0.0001, Gehan Breslow survival analysis). Survival from rigor and hypercontracture were not different in AA-NIR and AA-HDR groups while they were significantly higher in NA-NIR compared to NA-HDR group (p<0.0001, Gehan Breslow survival analysis). There was no difference in viability among the groups.
Conclusions: Substrate availability during ischemia ameliorates ischemia and reperfusion injury while hypercarbic delayed reoxygenation does not appear to be beneficial.
- © 2013 by American Heart Association, Inc.