Calreticulin (CRT) is a major Ca2+-binding chaperone mainly resident in the endoplasmic reticulum (ER) lumen.Recently,it has been shown that non-ER CRT regulates a wide array of cellular responses.We previously found that CRT was up-regulated during cardiomyocyte hypoxia/reoxygenation (H/R) and aimed to investigate whether CRT translocation from the ER to the nucleus aggravates ER stress-associated apoptosis during H/R in neonatal rat cardiomyocytes.Compared with control,H/R induced cell apoptosis and lactate dehydrogenase (LDH) leakage.