By autoradiography and in vivo PET imaging we identified regional CXCR4 upregulation in the infarct region peaking approximately at day 3 post MI, reaching a plateau phase followed by a steady and significant decline which was in good agreement to previously published data.23,27 Thackeray et al. reported a significantly increased I/R at day 3 as compared to the control group with a significant decline up to day 7.23 Li et al. investigated the CXCR4 expression in a rat ischemia-reperfusion model (I/R) with 125I-pentixather and found a maximum uptake 3 days after I/R. This evidence concerns the gene CXCR4 and ischemia.