TRANSIENT INHIBITION OF GLUCOSE-UPTAKE MIMICS ISCHEMIC PRECONDITIONING BY SALVAGING ISCHEMIC MYOCARDIUM IN THE RABBIT HEART

The aim of this study was to test whether transient inhibition of glucose uptake could precondition the rabbit heart. Rabbit hearts experienced 30 min regional ischemia followed by either 120 min (isolated heart protocol) or 180 min (in situ protocol) reperfusion. Infarct size was determined by tetrazolium staining. In isolated heart experiments, 15 min perfusion with glucose-free Krebs buffer starting 30 min prior to ischemia significantly limited infarct size to 9.9 +/- 2.6% of the risk zone as compared with 29.4 +/- 1.7% infarction in controls. This protection could be blocked (30.8 +/- 3.4%) by polymyxin B (50 mu M), a protein kinase C inhibitor, but not by 8-(p-sulfophenyl)theophylline, an adenosine receptor inhibitor, suggesting the mechanism was similar to that of ischemic preconditioning but without involvement of adenosine receptors. Pyruvate and acetate inhibit glucose uptake without incurring a metabolic deficit. When 20 mM pyruvate or 1 mM acetate was added to the glucose-containing buffer for 15 min prior to ischemia, protection was evident (12.0 +/- 3.0% and 10.0 +/- 3.7% infarction, respectively). However, when acetate (1 mM) was present in the perfusate throughout the experiment, neither omission of glucose nor addition of pyruvate caused protection (26.1 +/- 2.2% and 28.9 +/- 4.7% infarction, respectively). Furthermore, when in situ hearts which preferably utilize lipid substrates were treated with pyruvate (2 g/kg i.v. 20 min before ischemia), infarct size was 40.3 +/- 3.0%, which did not differ from that in untreated hearts (38.6 +/- 3.2%). Hence transient inhibition of glucose uptake can precondition the heart, but only if other substrates which are utilized in preference to glucose are absent. (C) 1995 Academic Press Limited