Myocardial Loss of Glutamate after Cold Chemical Cardioplegia and Storage in Isolated Blood-Perfused Pig Hearts

Abstract

Metabolic adaptation of the ischemic human heart includes release of lactate, augmented uptake of glucose and glutamate, together with increased release of citrate and alanine. In the present study exchanges of these metabolites were examined in relation to left ventricular function (LVF) in pig hearts during reperfusion after hypothermic cardioplegic-induced global ischemia and storage. Three groups of pig hearts were studied. Group I consisted of 11 hearts subjected to 9 minutes of warm ischemia prior to cold chemical cardioplegia with Bretschneider's cardioplegic solution (CCC), and hypothermic storage (HS), for a total of 180 minutes. Groups II and III, 8 hearts in each, were subjected to 90 and 180 minutes of CCC and HS, without precardioplegic warm ischemia. All hearts were reperfused in an isolated blood-perfused Langendorff model. Myocardial oxygen uptake and LVF were two-fold depressed in Group I compared to Groups II and III during the first 25 minutes of reperfusion. An increased uptake of glucose (p < 0.05) and augmented release of lactate (p < 0.01) and citrate (p < 0.001) were found during the reperfusion period in the hearts subjected to precardioplegic warm ischemia, indicating an increased total ischemic burden compared to Groups II and III. No significant changes in LVF or myocardial metabolism were noted between Groups II and III during reperfusion. In all three heart groups a substantial release or loss of glutamate was found at start of reperfusion, although in the preischemic state prior to cardioplegia pig hearts were found to extract glutamate from the circulation to an extent similar to that of the human heart.(ABSTRACT TRUNCATED AT 250 WORDS)