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Objective To investigate the effect and mechanism of different high concentrations glucose(Glu) on the expression of hypoxia-inducible factor 1α(HIF-1α) in cultured neonatal rat eardiomyocytes under hypoxia and non-hypoxia conditions. Methods Neonatal rat cardiomyocytes were cultured for 6 hours under different conditions and were divided into 6 groups:①Negative control group (5.5 mmol/L Glu) ; ②hypoxia mimicking cobalt chloride(Cocl_2) group(5.5 mmol/L Glu + 400 μmol/L cocl_2 ) ;③Different high concentrations Glu groups: (11.1 mmol/L, 22.2 mmol/L, 33.3 mmol/L Glu);④cocl_2 +different high concentrations Glu groups(11.1 mmol/L Glu +400 μmol/L cocl_2,22.2 mmol/L Glu +400 μmol/L cocl_2, 33.3 mmol/L Glu+400 μmol/L cocl_2);⑤High concentrations Glu + antioxidant α-tocopherol group(33.3 mmol/L Glu + 100 μmol/L α-tocopherol) ; ⑥ High concentrations Glu+antioxidant α-tocopherol+cocl_2 group(33.3 mmol/L Glu+400 μmol/L cocl_2+100 μmol/L α-tocopherol). The effect of high concentrations Glu, cocl_2 and high concentrations Glu plus cocl_2 on the expression of HIF- 1α mRNA and protein in cultured neonatal rat cardiomyocytes, as well as the effect of high concentrations Glu plus antioxidant α-tocopherol, high Glu concentrations plus cocl_2 and antioxidant α-tocopherol on the expression of HIF- 1α mRNA and protein were observed. Results 1. Compared with negative control group(5.5 mmol/L Glu), the 'expression of HIF- 1α was increased under cocl_2 mimicked hypoxia(5.5 mmol/L Glu+400 μmol/L cocl_2, 11.1 mmol/L Glu+400 μmol/L cocl_2 ,22.2 mmol/L Glu+400 μmol/L cocl_2,33.3 mmol/L Glu+400 μmol/L cocl_2). 2. The expression of HIF- 1α was increased gradually after the increasing of Glu concentrations(5.5 mmol/L, 11.1 mmol/L, 22.2 mmol/L and 33.3 mmol/L Glu).3.The expression of HIF-1α was decreased gradually after the increasing of Glu concentrations under certain cocl_2 plus different high concentrations Glu (5.5 mmol/L Glu+400 μmol/L cocl_2, 11.1 mmol/L Glu+400 μmol/L cocl_2, 22.2 mmol/L Glu+400 μmol/L cocl_2,33.3 mmol/L Glu+400 μmol/L cocl_2). 4. Under high concentration Glu plus antioxidant α-tocopherol (33.3 mmol/L Glu+100 μmol/L α-tocopherol) ,the expression of HIF- 1α was less increased than the same high Glu concentration(33.3 mmol/L Glu). 5. Under high Glu concentration plus cocl_2 (33.3 mmol/L Glu+400 μmol/L cocl_2), the expression of HIF- 1α increased less than that of the same high Glu concentration plus antioxidant α-tocopherol and cocl_2 (33.3 mmol/L Glu+400 μmol/L Cocl_2+ 100 μmol/L α-tocopherol). Conclusions High glucose increases the expression of HIF-1α under non-hypoxia, but blunts the expression of HIF-1α under hypoxia in cultured neonatal rat cardiomyocytes. Some mechanisms such as ROS (reactive oxygen species) signal transduction system and oxidative stress may be involved in it.