Impact of acute ischemia-reperfusion on myocardial mitochondrial function in an ex-vivo model of global myocardial ischemia.
BACKGROUND
Cardiac mitochondria, as the major source of energy used by the heart, play an important part in the survival of cardiomyocytes undergoing ischemia followed by reperfusion. During ischemia, cardiac mitochondria represent one of the main cellular defense mechanisms, acting as a calcium-sequestering system and maintaining levels of energy production. However, when these cellular mechanisms are overcome, loss of mitochondrial integrity leads not only to the breakdown of energy production, but also to the release of pro-apoptotic factors, thus compromising the survival of cardiac cells.


OBJECTIVE
To study the impact of acute ischemia-reperfusion (IR) on myocardial mitochondrial function in an ex-vivo model of global ischemia.


METHODS
Wistar rat hearts were divided into two groups: control (165 minutes of perfusion with Krebs-Henseleit solution) and ischemia-reperfusion (IR - 10 minutes perfusion, followed by 35 minutes ischemia and 120 minutes reperfusion). Various parameters of mitochondrial function were assessed: respiratory control ratio (RCR) using a Clark-type oxygen electrode, oxidative stress (using the thiobarbituric acid reactive substances [TBARS] test), and mitochondrial swelling amplitude and calcium uptake, both determined by fluorimetric methods.


RESULTS
All mitochondrial parameters were severely affected by IR. The IR group showed a significant decrease in RCR, which was independent of the respiratory substrate used, for each assay. There were no significant differences between the two experimental groups in TBARS production. The control group showed a trend for a decrease in mitochondrial swelling amplitude and an increase in calcium uptake compared to the IR group, in both the absence and presence of cyclosporin A.


CONCLUSIONS
In this study, IR significantly altered mitochondrial function (RCR, mitochondrial swelling amplitude and intramitochondrial calcium uptake). This means that during acute myocardial ischemia, every effort should be made to avoid reperfusion injury, given its deleterious consequences for coronary artery disease patients.
Paiva
Marta A
MA
Unidade de Investigação Básica em Cardiologia, Serviço de Cardiologia, Hospitais da Universidade de Coimbra e Faculdade de Medicina da Universidade de Coimbra, Coimbra, Portugal.
Carreira
Raquel
R
Monteiro
Pedro
P
Gonçalves
Lino M
LM
Providência
Luís A
LA
D000208:Acute Disease; D000818:Animals; D008297:Male; D008929:Mitochondria, Heart / Q000378:metabolism*; D017202:Myocardial Ischemia / Q000378:metabolism*; D015428:Myocardial Reperfusion Injury / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar