Myocardial Pyruvate, Lactate, and Orthophosphate Contents Under Different Postischemic Conditions: A Study in a Paracorporeal Rat Heart Model

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Abstract
The myocardial contents of pyruvate, lactate and orthophosphate after ischemia were investigated in a paracorporeal rat heart model under different conditions. The arterial blood was supplemented with phosphoenolpyruvate (PEP) and adenosine triphosphate early during reperfusion of excised hearts subjected to 15 min of complete global ischemia at 37 degrees C. The increase in myocardial pyruvate was significant after 4 min of reperfusion compared with the content in non-supplemented hearts subjected to the same ischemic trauma. Such dynamic changes were not observed for lactate and orthophosphate under corresponding conditions. The distinct increase in myocardial pyruvate content on supplementation with PEP and adenosine triphosphate was most probably due to an adenosine triphosphate-mediated PEP translocation into myocardial cells, with rapid metabolization of translocated PEP into adenosine triphosphate (in the presence of cellular adenosine diphosphate) and pyruvate. The pyruvate and lactate relationship varied, depending on the postischemic conditions. The postischemic myocardial orthophosphate content was stable, with only minor fluctuations. This possibility to supply the postischemic myocardium with substrate for immediate intracellular energy production is of clinical interest and merits further studies.