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Oxidative damage from elevated production of reactive oxygen species (ROS) contributes to ischemia-reperfusion injury in myocardial infarction and stroke. The mechanism by which the increase in ROS occurs is not [...]

Pre- and postconditioning depend on the activation of adenosine receptors (ARs) at the end of the index ischemia. The aim of this study was to determine which receptor subtypes must be activated. In situ mouse hearts underwent 30 min of regional ischemia, followed by 2 h of reperfusion. As expected, either ischemic postconditioning (6 cycles of 10 s of reperfusion and 10 s of coronary occlusion) or infusion of the selective [A.sub.2b] adenosine receptor ([A.sub.2b]AR) agonist BAY60-6583 (BAY60) for 60 min, starting 5 min before reperfusion reduced infarct size in wild-type C57B1/6N mice. Protection from either was abolished by the selective [A.sub.2b]AR antagonist MRS-1754, confirming a role for [A.sub.2b]AR. Additionally, the coadministration of ischemic postconditioning and a selective [A.sub.2a]AR antagonist led to the loss of protection as well. 5'-Ectonucleotidase (CD73) is thought to be necessary for the production of adenosine during ischemia. As predicted, ischemic postconditioning did not protect CD73 knockout mice. Selective agonists of either [A.sub.2b]AR (BAY60) or [A.sub.2a]AR (CGS-21680), as well as the coadministration of ischemic postconditioning and BAY60, also failed to protect hearts of the CD73 knockout mice. But the nonselective [A.sub.1]/[A.sub.2]AR agonist 5'-(N-ethylcarboxamido)adenosine (NECA) was protective, suggesting that the activation of multiple AR subtypes might be required. The coadministration of CGS-21680 and BAY60 also elicited profound protection, indicating that two AR subtypes, [A.sub.2a] and [A.sub.2b], must be simultaneously activated for protection to occur. cardioprotection; 5'-ectonucleotidase; postconditioning; reperfusion doi: 10.1152/ajpheart.00181.2010.

Pre- and postconditioning depend on activation of adenosine receptors at the end of the index ischemia. The aim of this study was to determine which receptor subtypes must be activated. In situ mouse hearts underwent 30 min of regional ischemia followed by 2 h of reperfusion. As expected, either ischemic postconditioning (six cycles of 10 sec of reperfusion and 10 sec of coronary occlusion) or infusion of the selective A2b adenosine receptor (A2bAR) agonist BAY60-6583 (BAY60) for 60 min starting 5 min prior to reperfusion reduced infarct size in wild-type C57Bl/6N mice. Protection from either was abolished by the selective A2bAR antagonist MRS1754 confirming a role for A2bAR. Additionally, co-administration of ischemic postconditioning and a selective A2aAR antagonist led to loss of protection as well. CD73 (5′-ectonucleotidase) is thought to be necessary for the production of adenosine during ischemia. As predicted, ischemic postconditioning did not protect CD73 knock-out mice. Selective agonists of either A2bAR (BAY60) or A2aAR (CGS-21680) as well as co-administration of ischemic postconditioning and BAY60 also failed to protect hearts of the CD73 knock-out mice. But the non-selective A1/AAR agonist 5′-(N-ethylcarboxamido) adenosine (NECA) was protective suggesting that activation of multiple AR subtypes might be required. Co-administration of CGS-21680 and BAY60 also elicited profound protection, indicating two AR subtypes, A2a and A2b, must be simultaneously activated for protection to occur. [ABSTRACT FROM AUTHOR]