Ischemic preconditioning limits infarct size following regional ischemia–reperfusion in in situ mouse hearts

OBJECTIVE: Ischemic preconditioning has been demonstrated in a wide variety of animals, from dogs to rats. Experimentally-induced murine myocardial ischemia-reperfusion has been described, but ischemic preconditioning has not been reported in mouse hearts. To test the hypothesis that mouse hearts exhibit preconditioning-induced protection, experiments were conducted in anesthetized open chest mice subjected to regional myocardial ischemia-reperfusion. METHODS: Following barbiturate anesthesia the FVB and C57BL/6J mice underwent a tracheostomy and were mechanically ventilated. The heart was exposed via a left thoracotomy performed with the aid of a dissecting microscope. A 7-0 silk suture on a curved taper needle was passed under the proximal left anterior descending coronary artery to form a snare. Mice were then randomly assigned to receive either no preconditioning or preconditioning. All mice were subjected to 60 min regional myocardial ischemia followed by 2.5 h of reperfusion. Ischemic preconditioning (IP) was induced with two (FVB mice) or three (C57BL/6J mice) cycles of 5 min coronary occlusion and 5 min reperfusion. Control animals did not receive preconditioning ischemia. Area-at-risk was assessed with fluorescent particles. Infarct size was assessed with triphenyl tetrazolium chloride, and is expressed below as a percentage of the area-at-risk. RESULTS: In FVB mice preconditioning reduced infarct size 49%, from 36.7 +/- 4.5% to 18.9 +/- 2.8% (P < 0.05). In C57BL/6J mice preconditioning reduced infarct size by 66%, from 56.4 +/- 8.3% to 18.9 +/- 4.2% (P < 0.05). CONCLUSION: From these data we conclude that the infarct limiting effect of ischemic preconditioning is demonstrable in murine hearts.