Ischémie preconditioning in pigeon hearts

Ischémie preconditioning has been shown to occur in a number of species and different preparations, but studies to date have concentrated on mammals. Pigeon hearts, which contain a high density of KATP channels, were removed from animals anesthetized with pentobarbital and perfused with Krebs-Henseleit bicarbonate buffer with 1,25 mM Ca" at a pressure of 60 cm H2O and paced at 240 beats per min After an equilibration perfusion of 30 min, hearts were subjected to 10 min global ischemia and then reperfused for 30 min. Left ventricular systolic and diastolic pressures differed significantly from baseline values during reperfusion as did the release of lactate dehydrogenase, (LDH). When the hearts were preconditioned by interruption of flow for two 2.5 min intervals followed by 10 min of ischemia and then reperfusion, the short periods of ischemia followed by reperfusion protected the hearts against the longer bout of ischemia as evidenced by significant differences between the pressure and LDH values obtained from the hearts of control vs preconditioned hearts The effect of preconditioning disappeared when 1 M glibenclamide (KArp channel antagonist) was included in the perfusion buffer. Buffer with vehicle (DMSO) did not block preconditioning. Substitution of 1 nM lemakalim, a K ATP channel agonist, for preconditioning resulted in ventricular fibrillation rather than protection against ischemia Isolated, perfused perfused bird hearts can be preconditioned and the mechanism appears to involve K_ATP-Channels.