Adenosine-enhanced ischemic preconditioning (APC) extends the cardioprotection of ischemic preconditioning (IPC) by both significantly decreasing
myocardial infarct size and significantly enhancing postischemic functional recovery. In this study, the role of
adenosine receptors during
ischemia-reperfusion was determined. Rabbit hearts (n = 92) were used for Langendorff perfusion. Control hearts were perfused for 180 min, global
ischemia hearts received 30-min
ischemia and 120-min reperfusion, and IPC hearts received 5-min
ischemia and 5-min reperfusion before
ischemia. APC hearts received a bolus injection of
adenosine coincident with IPC.
Adenosine receptor (A(1), A(2), and A(3)) antagonists were used with APC before
ischemia and/or during reperfusion. GR-69019X (A(1)/A(3)) and
MRS-1191/
MRS-1220 (A(3)) significantly increased
infarct size in APC hearts when administered before
ischemia and significantly decreased functional recovery when administered during both
ischemia and reperfusion (P < 0.05 vs. APC).
DPCPX (A(1)) administered either before
ischemia and/or during reperfusion had no effect on APC cardioprotection. APC-enhanced
infarct size reduction is modulated by
adenosine receptors primarily during
ischemia, whereas APC-enhanced postischemic functional recovery is modulated by
adenosine receptors during both
ischemia and reperfusion.