The heat shock protein 70 and glucose-regulated protein 78 have been shown to protect cells against deleterious stimuli. This study was performed to determine whether endothelin-1 pretreatment could increase cardiomyocyte tolerance to hypoxia and induce heat shock protein 70 and glucose-regulated protein 78 expression. Cultured cardiomyocytes were treated with endothelin-1 at doses of 0.01, 0.1 and 1.0 nmol/L for 10 minutes followed by 10 minutes endothelin-1-free normal medium prior to 12 hours hypoxia. Lactate dehydrogenase activity and malondialdehyde level in the medium were determined at the end of hypoxia, and myocyte heat shock protein 70 and glucose-regulated protein 78 were assayed with Western blot. Lactate dehydrogenase activity and malondialdehyde content in the medium were significantly elevated after hypoxia (P < 0.01, n = 6). Heat shock protein 70 and glucoseregulated protein 78 expression in cardiomyocytes also increased significantly after hypoxia (P < 0.01 vs control, n = 3). Endothelin- 1 pretreatment reduced lactate dehydrogenase and malondialdehyde after hypoxia, and increased heat shock protein 70 and glucoseregulated protein 78 levels during normal culture and hypoxia. Glucose-regulated protein 78 antisense oligodeoxynucleotide partially abrogated the protective effect of endothelin-1 pretreatment on hypoxic cardiomyocyte injury. This study indicated that endothelin-1 pretreatment could protect hypoxic cardiomyocytes and might exert this effect through upregulation of heat shock protein 70 and glucose-regulated protein 78.