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Differences in ischemia-reperfusion-induced endothelial changes in hearts perfused at constant flow and constant
Raja B Singh1, Vijayan Elimban, Naranjan S Dhalla
1Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, 351 Tache Ave., Winnipeg, Manitoba, Canada R2H 2A6.
Insights
Ischemia-reperfusion injury causes greater cardiac dysfunction in hearts perfused at constant flow (CF) versus constant pressure (CP). This difference is linked to more significant endothelial dysfunction and altered subcellular function in CF-perfused hearts.
Area of Science:
- Cardiovascular Physiology
- Ischemia-Reperfusion Injury
- Cardiac Mechanics
Background:
- Ischemia-reperfusion (I/R) injury impairs cardiac performance and subcellular functions.
- Differences in contractile responses to I/R exist between constant flow (CF) and constant pressure (CP) perfusion methods.
Purpose of the Study:
- To investigate the mechanisms behind I/R-induced alterations in CF-perfused and CP-perfused rat hearts.
- To compare cardiac function, sarcolemmal Na(+)-K(+)-ATPase activity, sarcoplasmic reticulum Ca(2+) uptake, and endothelial function between CF and CP perfusion during I/R.
Main Methods:
- Isolated rat hearts were perfused at either CF (10 ml/min) or CP (80 mmHg).
- Hearts underwent 30 minutes of global ischemia followed by 60 minutes of reperfusion.
- Cardiac function, sarcolemmal Na(+)-K(+)-ATPase activity, sarcoplasmic reticulum Ca(2+) uptake, calpain activity, and endothelial nitric oxide synthase (eNOS) protein content were assessed.
Main Results:
- I/R caused greater depression in cardiac function, SL Na(+)-K(+)-ATPase, and SR Ca(2+) uptake in CF-perfused hearts compared to CP-perfused hearts.
- CF-perfused hearts showed increased calpain activity, decreased eNOS protein, and reduced nitric oxide (NO) levels post-I/R compared to CP-perfused hearts.
- L-arginine attenuated I/R effects in CF hearts, while N(G)-nitro-l-arginine methyl ester exacerbated them in CP hearts.
Conclusions:
- Greater I/R-induced cardiac dysfunction in CF-perfused hearts is partly due to more pronounced endothelial dysfunction.
- Differences in perfusion methods significantly impact the response to I/R injury at both the organ and subcellular levels.
Abstract:
Isolated hearts subjected to ischemia-reperfusion (I/R) exhibit depressed cardiac performance and alterations in subcellular function. Since hearts perfused at constant flow (CF) and constant pressure (CP) show differences in their contractile response to I/R, this study was undertaken to examine mechanisms responsible for these I/R-induced alterations in CF-perfused and CP-perfused hearts. Rat hearts, perfused at CF (10 ml/min) or CP (80 mmHg), were subjected to I/R (30 min global ischemia followed by 60 min reperfusion), and changes in cardiac function as well as sarcolemmal (SL) Na(+)-K(+)-ATPase activity, sarcoplasmic reticulum (SR) Ca(2+) uptake, and endothelial function were monitored. The I/R-induced depressions in cardiac function, SL Na(+)-K(+)-ATPase, and SR Ca(2+)-uptake activities were greater in hearts perfused at CF than in hearts perfused at CP. In hearts perfused at CF, I/R-induced increase in calpain activity and decrease in nitric oxide (NO) synthase (endothelial NO synthase) protein content in the heart as well as decrease in NO concentration of the perfusate were greater than in hearts perfused at CP. These changes in contractile activity and biochemical parameters due to I/R in hearts perfused at CF were attenuated by treatment with l-arginine, a substrate for NO synthase, while those in hearts perfused at CP were augmented by treatment with N(G)-nitro-l-arginine methyl ester, an inhibitor of NO synthase. The results indicate that the I/R-induced differences in contractile responses and alterations in subcellular organelles between hearts perfused at CF and CP may partly be attributed to greater endothelial dysfunction in CF-perfused hearts than that in CP-perfused hearts.
