Increased glycolysis during ischaemia mediates the protective effect of glucose and insulin in the isolated rat heart despite the presence of cardiodepressant exogenous substrates : cardiovascular topics

Background : Exogenous insulin is known to protect against ischaemia-reperfusion injury of the myocardium. We investigated whether these benefits of insulin could be explained by increased glycolysis during the ishaemic period, even in the presence of potentially cardiodepressant substrates such as fatty acids and lactate. Increased cardiac output during post-ischaemic reperfusion was used as a marker of protection by insulin. Methods : Isolated hearts from fasted rats were subjected to 5 minutes of Langendorff perfusion followed by a 15-minute working heart pre-ischaemic perfusion with glucose (11 mmol/l), followed by a 30-minute 0. 2 ml/min low-flow Langendorff ischaemic period, using glucose (11 mmol/l) or glucose plus fatty acids (1 mmol/l), or lactate (10 mmol/l), or lactate plus glucose as substrates. During reperfusion, the hearts were again perfused with glucose. Insulin (1 mU/ml), when added, was present throughout the experimental protocol. Results : Post-ischaemic reperfusion cardiac output recovery was depressed in hearts perfused with glucose plus fatty acids or with lactate alone, when compared with glucose alone (p