ATP precursor depletion and postischemic myocardial recovery

Area of Science:

• Cardiology
• Biochemistry
• Physiology

Background:

• Cardioplegia reduces myocardial metabolism during ischemia but can lead to adenosine triphosphate (ATP) depletion.
• Augmenting myocardial adenosine during ischemia improves ATP repletion and functional recovery after reperfusion.
• Adenosine's role in ischemic tolerance suggests its depletion negatively impacts cardiac recovery.

Purpose of the Study:

• To investigate the impact of myocardial adenosine depletion on functional and metabolic recovery following ischemia.
• To test the hypothesis that myocardial adenosine levels are critical determinants of ischemic tolerance.

Main Methods:

• Isolated, perfused rabbit hearts subjected to 120 minutes of 34°C global ischemia.
• Hearts treated with St. Thomas cardioplegia alone, cardioplegia with adenosine, or cardioplegia with varying doses of adenosine deaminase (ADA).
• Functional recovery (developed pressure) and myocardial nucleotide levels (ATP) were measured before, during, and after ischemia.

Main Results:

• Adenosine-augmented hearts showed significantly better recovery (68% of preischemic developed pressure) compared to controls (51%).
• Adenosine deaminase (ADA) treatment significantly impaired recovery, with hearts receiving 0.025 µg/ml ADA recovering to only 29% of developed pressure.
• ADA treatment led to depleted ATP and precursor reserves, while adenosine enhanced metabolic recovery.

Conclusions:

• Myocardial adenosine levels at the end of ischemia and during early reperfusion are crucial determinants of functional recovery.
• Eliminating adenosine via ADA significantly compromises both functional and metabolic recovery after global ischemia.
• Maintaining adenosine availability is vital for preserving myocardial energy status and improving cardiac function post-ischemia.