ATP-regulated K+ channels are involved in anesthetic-induced preconditioning (APC). The role of other K+ channels in APC is unclear. We tested the hypothesis that APC is mediated by large-conductance calcium-activated K+ channels (KCa).METHODS:
Pentobarbital-anesthetized male C57BL/6 mice were subjected to 45 min of coronary artery occlusion and 3 h reperfusion. Thirty minutes before coronary artery occlusion, 1.0 MAC desflurane was administered for 15 min alone or in combination with the large-conductance KCa channel activator NS1619 (1 μg/g i.p.), its respective vehicle dimethylsulfoxide (10 μL/g i.p.), the large-conductance KCa channel blocker iberiotoxin (0.05 μg/g i.p.), or the protein kinase A (PKA) inhibitor H-89 (0.5 μg/g intraventricular). Infarct size was determined with triphenyltetrazolium chloride and area at risk with Evans blue. Mitochondrial and sarcolemmal localization of large-conductance KCa channels in cardiac myocytes was investigated with immunocytochemical staining of isolated cardiac myocytes.RESULTS:
Desflurane significantly reduced infarct size compared with control animals (7.4% ± 0.8% vs 51.3% ± 6.1%; P < 0.05). Activation of large-conductance KCa channels by NS1619 (7.5% ± 1.8%; P < 0.05) mimicked and blockade of large-conductance KCa channels by iberiotoxin (49.1% ± 7.5%) abrogated desflurane-induced preconditioning. PKA blockade by H-89 abolished desflurane-induced (45.1% ± 4.0%) but not NS1619-induced (9.0% ± 2.4%, P < 0.05) preconditioning. Immunocytochemical staining revealed that large-conductance KCa channels were localized in the mitochondria but not in the sarcolemma of cardiac myocytes.CONCLUSION:
These data suggest that desflurane-induced APC is mediated in part by activation of mitochondrial large-conductance KCa channels, and that activation of these channels by desflurane is mediated by PKA.