Moderate glucose deprivation preconditions myocardium against infarction

Glucose-free perfusion preconditions myocardium against the consequences of subsequent ischemia. We investigated whether mitochondrial ATP-sensitive potassium (mK(ATP)) channels are involved in preconditioning by glucose deprivation, and whether moderate glucose deprivation also preconditions myocardium. Isolated rat hearts underwent 30 min of no-flow ischemia followed by 1 h reperfusion. Controls were not further treated. Three groups were preconditioned by perfusion with 0, 40 or 80 mg/dl (0, 2.22, 4.44 mmol/l) glucose (correction of osmotic pressure by addition of urea) for 10 min followed by 10 min perfusion with normal buffer (150 mg/dl, or 8.33 mmol/l glucose) before the ischemia reperfusion protocol. in one group, 100 pmol/l of the mK(ATP) channel blocker 5-HD was added to the glucose-free perfusate. Two groups were treated with 5-HD or urea before ischemia without preconditioning. Left ventricular developed pressure and maximum ischemic contracture (82 +/- 21 mmHg) were similar in all groups. Mean left ventricular developed pressure was 100 +/- 16 mm Hg under baseline conditions, and poorly recovered to 8 +/- 11 mm Hg during reperfusion. Preconditioning with 0 and 40 mg/dl glucose containing buffer reduced infarct size from 41 +/- 10% (control) to 23 +/- 12% (p = 0.02) and 26 +/- 8 % (p = 0.011). The 5-HD blocked preconditioning by glucose deprivation (38 9 %, p = 0.04) while 80 mg/dl glucose, 5-HD and urea had no effect on infarct size (39 9 %; 38 +/- 13 %: 37 +/- 8 %; p = 1.0 each). We conclude that transient severe glucose deprivation and moderate glucose deprivation preconditions the isolated rat heart. Preconditioning by complete glucose deprivation depends on the opening of mK(ATP) channels.