Attenuation of myocardial stunning by an increase in the H+ buffering capacity of the perfusate and that by hypoxic preperfusion are affected differently by the free (Ca2+) of the perfusate.

Isolated rat hearts

Preperfusion with oxygenated buffer containing 100 mM HEPES or hypoxic buffer for 10 min, with varying free Ca2+ concentrations (1.25 mM or 2.5 mM), followed by 15 min of total ischemia and 30 min of reperfusion

Preperfusion with oxygenated buffer containing 100 mM sucrose

Metabolic and functional recovery, accumulation of intracellular Na+ during ischemia, and 45Ca2+ uptake during reperfusionsurrogate