[The protective effects of glucose in ischaemia, anoxia and reoxygenation (author's transl)]

In the present study we used a model of underperfusion or anoxia followed by reperfusion to assess the role of glycolysis by substituting pyruvate or mannitol for glucose as substrate. Hearts were removed from male Sprague-Dawley rats (250-400 g) and perfused by the technique of Langendorff. The perfusate was Krebs-Henseleit bicarbonate buffer gassed with 95% O2, 5% CO2 or with 95% N2, 5% CO2 mixture and containing substrates as can be seen in the figures. The mild ischemia was obtained by reducing the perfusion pressure by 70%, from 60-70 cm H2O to 10-20 cm H2O. The coronary flow was rapidly reduced to 0.8 +/- 0.03 ml/min within the first 5 minutes. After mild ischemia anaerobic glycolysis was accelerated because lactate production in ischemic hearts perfused with glucose (36.2 +/- 15.3 microM/g/min-1) was higher than in the ischemic hearts perfused with mannitol (6.8 +/- 1.9 microM/g/min-1). During mild ischemia or anoxia there was little difference in the rate of release of creatin-kinase for all the substrates tested, but major differences become apparent on reperfusion. In that period the highest values of CK release were found in mannitol perfused hearts, the lowest in glucose perfused hearts. These results suggest that the rate of glycolytic flux during mild ischemia or anoxia may prevent enzyme release. The beneficial effect of glucose has been observed also during reperfusion. In fact enzyme release was higher in hearts reperfused with glucose than with pyruvate. When pyruvate is the only exogenous substrate available for isolated oxigenated hearts, tissue levels of citric acid cycle intermediates are high and oxidation of these substrates can account for 100% of the oxygen consumption. Therefore we suppose that oxidation of noncarbohydrate substrates such as pyruvate in reperfusion is complicated by the high mitochondrial damage. As a consequence anaerobic glycolytic pathway may play a special role in the maintenance of the membrane integrity also in the early phases of reperfusion.