High energy phosphate stores and lactate levels in different layers of the canine left ventricle during reactive hyperemia.

To study postischemic recovery of myocardial energy metabolism in relation to the reactive hyperemic response, the tissue levels of creatine phosphate (CP), adenosine triphosphate (ATP), and lactate were estimated in the outer, middle, and inner layers of the left ventricle before, during, and at several times after a 20-second bilateral coronary arterial occlusion in the open-chest dog. The reactive hyperemic response was characterized by monitoring blood flow in the cannulated coronary sinus in a separate group of dogs. Substantial changes in myocardial CP and lactate, but not ATP, were produced by the occlusion and reciprocal transmural gradients in CP and lactate occurred such that CP was lowest and lactate was highest in the inner layer. Recovery of high energy phosphate stores (CP + ATP) occurred long before blood flow returned to the preocclusion level, this being achieved in two of the three layers after completion of only 29% of the reactive hyperemic response when the blood flow debt repayment was 151%. Lactate returned to control levels during the response, but recovery times in the different layers were delayed compared to those for the high energy phosphate stores. A transmural lactate gradient was maintained as the regional levels declined, and recovery times were different for each of the three layers, being longest in the inner layer. The results suggest that during the reactive hyperemic response (1) kinetically different processes are involved in the repletion of energy stores and the removal of anaerobically produced metabolites, and (2) metabolic vasodilation of coronary vessels probably is more pronounced and sustained longer in the inner than in the outer ventricular layer.