Delayed cardioprotection by isoflurane: role of KATP channels

Abstract

Isoflurane mimics the cardioprotective effect of acute ischemic preconditioning with an acute memory phase. We determined whether isoflurane can induce delayed cardioprotection, the involvement of ATP-sensitive potassium (KATP) channels, and cellular location of the channels. Neonatal New Zealand White rabbits at 7–10 days of age ( n = 5–16/group) were exposed to 1% isoflurane-100% oxygen for 2 h. Hearts exposed 2 h to 100% oxygen served as untreated controls. Twenty-four hours later resistance to myocardial ischemia was determined using an isolated perfused heart model. Isoflurane significantly reduced infarct size/area at risk (means ± SD) by 50% (10 ± 5%) versus untreated controls (20 ± 6%). Isoflurane increased recovery of preischemic left ventricular developed pressure by 28% (69 ± 4%) versus untreated controls (54 ± 6%). The mitochondrial KATP channel blocker 5-hydroxydecanoate (5-HD) completely (55 ± 3%) and the sarcolemmal KATPchannel blocker HMR 1098 partially (62 ± 3%) attenuated the cardioprotective effects of isoflurane. The combination of 5-HD and HMR-1098 completely abolished the cardioprotective effect of isoflurane (56 ± 5%). We conclude that both mitochondrial and sarcolemmal KATP channels contribute to isoflurane-induced delayed cardioprotection.