Background: Prevailing data suggest that ATP-sensitive potassium channels (K-ATP) contribute to a surprising resistance to hypoxia in mammalian embryos, thus we aimed to characterize the developmental changes of K-ATP channels in murine fetal ventricular cardiomyocytes. Methods: Patch clamp was applied to investigate the functions of K-ATP. RT-PCR, Western blot were used to further characterize the molecular properties of K-ATP channels. Results: Similar K-ATP current density was detected in ventricular cardiomyocytes of late development stage (LDS) and early development stage (EDS). Molecular-biological study revealed the upregulation of Kir6.1/SUR2A in membrane and Kir6.2 remained constant during development. Kir6.1. Kir6.2, and SUR1 were detectable in the mitochondria without marked difference between EDS and LDS. Acute hypoxia-ischemia led to cessation of APs in 62.5% of tested EDS cells and no APs cessation was observed in LDS cells. SarcK(ATP) blocker glibenclamide rescued 47% of EDS cells but converted 42.8% of LDS cells to APs cessations under hypoxia-ischemic condition. MitoK(ATP) blocker 5-HD did not significantly influence the response to acute hypoxia-ischemia at either EDS or LDS. In summary, sarcK(ATP) Played distinct functional roles under acute hypoxia-ischemic condition in EDS and LDS fetal ventricular cardiomyocytes, with developmental changes in sarcK(ATP) subunits. MitoK(ATP) were not significantly involved in the response of fetal cardiomyocytes to acute hypoxia-ischemia and no developmental changes of K-ATP subunits were found in mitochondria. (C) 2012 Elsevier Inc. All rights reserved.