Prevention of isoflurane-induced preconditioning by 5-hydroxydecanoate and gadolinium -: Possible involvement of mitochondrial adenosine triphosphate-sensitive potassium and stretch-activated channels

Background: Both mitochondrial adenosine triphosphate-sensitive potassium (MKATP) channels (selectively blocked by 5-hydroxydecanoate) and stretch-activated channels (blocked by gadolinium) have been Involved in the mechanism of ischemic preconditioning, Isoflurane can reproduce the protection afforded by ischemic preconditioning, We sought to determine whether isoflurane-induced preconditioning may involve MKATP and stretch-activated channels. Methods: Anesthetized open-chest rabbits underwent 30 min of coronary occlusion followed by 3 h of reperfusion, Before this, rabbits were randomized into one of six groups and underwent a treatment period consisting of either no intervention for 40 min (control group; n = 9) or 15 min of isoflurane inhalation (1.1% end tidal) followed by a 15-min washout period (isoflurane group; n = 9). The two groups received an intravenous bolus dose of either 5-hydroxydecanoate (5 mg/kg) or gadolinium (40 mu mol/kg) before coronary occlusion and reperfusion (5-hydroxydecanoate n = 9; gadolinium, n = 7), Two additional groups received 5-hydroxydecanoate or gadolinium before isoflurane exposure (isoflurane-5-hydroxydecanoate, n = 10; isoflurane-gadolinium, n = 8). Area at risk and infarct size were assessed by blue dye injection and tetrazolium chloride staining. Results: Area at risk was comparable among the six groups (29 +/- 7, 30 +/- 5, 27 +/- 6, 35 +/- 7, 31 +/- 7, and 27 +/- 4% of the left ventricle in the control, isoflurane, isoflurane-5-hydroxydecanoate, 5-hydroxydecanoate, isoflurane-gadolinium, and gadolinium groups, respectively). Infarct size averaged 60 +/- 20% (SD) in untreated controls versus 54 +/- 27 and 65 +/- 15% of the risk zone in 5-hydroxydecanoate- and gadolinium-treated controls (P = nonsignificant), in contrast, Infarct size in the isoflurane group was significantly reduced to 26 +/- 11% of the risk zone (P < 0.05 vs. control). Both 5-hydroxydecanoate and gadolinium prevented this attenuation: infarct size averaged 68 +/- 23 and 56 +/- 21% of risk zone in the isoflurane-5-hydroxydecanoate and isoflurane-gadolinium groups, respectively (P = nonsignificant vs. control). Conclusion: 5-Hydroxydecanoate and gadolinium inhibited pharmacologic preconditioning by Isoflurane. This result suggests that MKATP channels and mechanogated channels are probably involved in this protective mechanism.