ATP-sensitive K＋ channels (KATP) are major component of preventing ischemia-reperfusion injury. However, there is little information regarding to the expressional difference of KATP and its function between left and right ventricles. In this study, we measured the lactate dehydrogenase release of rabbit heart slices in vitro and determined the difference of the KATP expression at the both ventricles by measuring the level of KATP-forming Kir6.2 (OcKir6.2) mRNA using in situ hybridization. The hearts were preconditioned with 15 min hypoxia and reoxygenated for 15 min before a hypoxic period of 60 min, followed by reoxygenation for 180 min. With hypoxic preconditioning (100% N2) with 15 min, left ventricles (LV) showed higher release of LDH comparing with right ventricles (RV). Adding KATP blocker glibenclamide (10ՌM) prior to a hypoxic period of 60 min, hypoxic preconditioning effect of RV was more abolished than LV. With in situ hybridization, the optical density of OcKir6.2 was higher in RV. Therefore, we suggest that different KATP expression between LV and RV is responsible for the different response to hypoxia and hypoxic preconditioning of rabbit hearts.