Isoflurane-induced postconditioning via mitochondrial calcium-activated potassium channels.

PURPOSE Activation of the mitochondrial calcium-activated potassium (mKCa) channel reportedly confers resistance to myocardial ischemic stress. However, the role of the mKCa channel in postconditioning induced by volatile anesthetic remains unclear. METHODS Male Japanese white rabbits underwent coronary artery occlusion for 30 min followed by reperfusion for 3 h. Volatile anesthetic, isoflurane, was administered at 3 min prior to reperfusion for 5 min. Rabbits were injected with the mKCa channel blocker, iberiotoxin, or the mKCa channel opener, NS1619, at 8 min prior to reperfusion. Myocardial infarct size and the area at risk (AAR) were measured at the end of the experiment. RESULTS Isoflurane significantly reduced infarct size (23.0 ± 9.8% of the AAR, P<0.05) compared with the control (44.0 ± 9.1%). Iberiotoxin abolished the cardioprotective impact of isoflurane (43.0 ± 11.6%), while iberiotoxin alone exerted no effect on infarct size (45.0 ± 9.5%). NS1619 and isoflurane/NS1619 both significantly reduced infarct size (21.0 ± 10.3% and 19.0 ± 8.8%, respectively, P<0.05 vs control group), but isoflurane/NS1619 showed no additional benefits compared with isoflurane alone. CONCLUSION These results indicate that activation of the mKCa channel contribute isoflurane-induced postconditioning.