The intracellular Ca2? concentration ([Ca2?]i) isincreased during cardiac ischemia/reperfusion injury (IRI),leading to endo(sarco)plasmic reticulum (ER) stress. PersistentER stress, such as with the accumulation of [Ca2?]i,results in apoptosis. Ischemic post-conditioning (PC) canprotect cardiomyocytes from IRI by reducing the [Ca2?]i via protein kinase C (PKC). The calcium-sensing receptor(CaR), a G protein-coupled receptor, causes the productionof inositol phosphate (IP3) to increase therelease of intracellular Ca2? from the ER. This processcan be negatively regulated by PKC through the phosphorylationof Thr-888 of the CaR. This study testedthe hypothesis that PC prevents cardiomyocyte apoptosisby reducing the [Ca2?]i through an interaction of PKCwith CaR to alleviate [Ca2?]ER depletion and [Ca2?]melevation by the ER-mitochondrial associated membrane(MAM). Cardiomyocytes were post-conditioned after 3 hof ischemia by three cycles of 5 min of reperfusion and5 min of re-ischemia before 6 h of reperfusion. DuringPC, PKCe translocated to the cell membrane and interactedwith CaR. While PC led to a significant decreasein [Ca2?]i, the [Ca2?]ER was not reduced and [Ca2?]mwas not increased in the PC and GdCl3–PC groups.Furthermore, there was no evident Dwm collapse duringPC compared with ischemia/reperfusion (I/R) or PKCinhibitor groups, as evaluated by laser confocal scanningmicroscopy. The apoptotic rates detected by TUNEL andHoechst33342 were lower in PC and GdCl3–PC groupsthan those in I/R and PKC inhibitor groups. Apoptoticproteins, including m-calpain, BAP31, and caspase-12,were significantly increased in the I/R and PKC inhibitorgroups. These results suggested that PKCe interactingwith CaR protected post-conditioned cardiomyocytes fromprogrammed cell death by inhibiting disruption of themitochondria by the ER as well as preventing calciuminducedsignaling of the apoptotic pathway.