Objective To investigate the protective mechanism of protein kinase C(PKC)and calcium sensing receptor(CaR)in ischemia preconditioned rat hearts.Methods Using cell culture method,in vitro cultured inhibitor(IPC+CaRI).Apoptosis was detected using TUNEL and Hoechst33342 cell viability was detected by MTT,the protein expression of easpase-12,calpain and CaR in endochylema were detected using Wedtetm blot.ResultsIn I/R group nucleus was shrank,big blue,chromatin concentrated,apoptotle body appeared.Other groups haddifferent fluorescence intensity varying degree,IPC+PKCI+CaRS group had more big blue nucleus.Myocardialcell viability and apoptotic rate,I/R group[(62.99±0.65)%,(19.13±0.87)%],IPC group[(78.67±0.37)%,(14.21±0.74)%],IPC+PKCI group[(71.09±0.52)%,(20.46±0.81)%],IPC+PKCI+CaRS group(66.10±0.75)%,(24.89±1.43)%],IPC+CaRS group[(69.56±0.44)%,(21.64±0.77)%],IPC+CaRI group(85.81±0.60)%,(13.12±0.69)%],all had a difference(P＜0.05 or＜0.01)compared with C group[(100.00)%,(6.02±0. 31)%].Western blot identified that CaR expression in IPC+PKCI and IPC+CaRS,IPC+PKCI+CaRS groupswas more than that in IPC and IPC+CaRI groups;easpase-12 had more active fragment(60×103)in I/R,IPC+CaRS,IPC+PKCI+CaRS groups;ealpain expressions in I/R,IPC,IPC+PKCI,IPC+PKCI+CaRS,IPC+CaRSgroups were higher than those in C and IPC+CaRI,I/R group was the highest one,C group the second,IPC+CaRI the third.Conclusion The interaction of PKC and CaR can reduce the intracellular Ca2+ from sarcoplasmicreticulum thus provide a protection.