Objective: To determine the effects of cytosolic calreticulin (CRT) on microwave radiation (MR)-induced myocardial microvascular endothelial cell (MMEC) injury, and the underlying mechanism.Methods: MMECs were randomized into eight groups: control, AdCRT (infected with pAdCMV/V5-DEST-CRT adenovirus), stCRT (transfected with rCRT-siRNAs), Mock (transfected with scrambled siRNAs), MR (exposed to microwave radiation for 6 minutes), AdCRT + MR, stCRT + MR, and Mock + MR.The magnitude of cell injury, were assessed by AnnexinV-PI staining, lactate dehydrogenase (LDH) activity in culture medium, MMEC migration ability, ultrastructure and cytoskeletal stability.Subcellular colocalization of CRT and concanavalin A or integrin were evaluated by immunocytochemistry.The mRNA and protein expression levels of target genes were examined by qRT-PCR and Western blotting, respectively.Results: MR-induced cytotoxicity was dose-dependent.Overexpression of cytosolic CRT suppressed MR injury, shown as decreased cell apoptosis, reduced LDH activity, enhanced cell migration capability, and maintenance of ultrastructure and cytoskeleton integrity.Conversely, CRT deficiency aggravated MR-induced injury.Exposure of AdCRT MMECs to MR promoted membrane translocation of CRT and the interaction of CRT-integrin-α.Correlation analysis revealed that integrin-α expression or FAK phosphorylation was positively associated with cytosolic CRT expression.Conclusions: Cytosolic CRT; inhibits MR-induced; MMEC; injury through ;activation of the integrin-FAK pathway