Adenosine endogenously released during early reperfusion mitigates postischemic myocardial dysfunction by inhibiting...

Area of Science:

• Cardiovascular Physiology
• Hematology
• Pharmacology

Background:

• Platelets play a role in cardiovascular events, including those following ischemia.
• Adenosine signaling is crucial in regulating vascular function and inflammation.

Purpose of the Study:

• To investigate the impact of platelets on post-ischemic heart function.
• To examine the role of adenosine in modulating intracoronary platelet adhesion during ischemia and reperfusion.

Main Methods:

• Isolated guinea pig hearts were subjected to low-flow ischemia and reperfusion.
• Homologous platelets were infused, with or without thrombin, during different phases.
• External heart work (EHW) and intracoronary platelet adhesion were measured.
• Pharmacological agents (dipyridamole, theophylline, DPCPX, DMPX, NOLAG, indomethacin) were used to modulate adenosine and related pathways.

Main Results:

• Platelet infusion with thrombin during ischemia significantly reduced EHW recovery compared to controls.
• Platelet adhesion was highest during ischemia with thrombin and during the fifth minute of reperfusion.
• Endogenous adenosine, modulated by dipyridamole, attenuated platelet adhesion during reperfusion.
• Theophylline, DPCPX, and DMPX influenced platelet adhesion, indicating roles for both A1 and A2 adenosine receptors.

Conclusions:

• Intracoronary platelet adhesion, particularly when induced by thrombin, impairs post-ischemic heart function recovery.
• Endogenous adenosine significantly mitigates platelet adhesion and preserves heart function during reperfusion, acting via both A1 and A2 receptors.
• Nitric oxide and prostaglandin I2 pathways were not found to be critical in this model.