Abstract: Objective To study the effect of naringin (NAR) on endoplasmic reticulum (ER) stress in cardiomyocytes injured by H9c2 hypoxia/reoxygenation (H/R).Methods H9c2 cardiomyocytes were randomly divided into three groups: control group, hypoxia/ reoxygenation group (H/R) for 24 h after hypoxia for 4 h, naringin 10, 20 and 40 μg /mL groups.Naringin was cultured 6 h before hypoxia for 4 h and then reoxygenation for 24 h. TUNEL detects apoptosis of cardiomyocytes after the experiment. Western blot was used to detect the expression of GRP78,ATF6,Bax and Bcl-2.Results Compared with control group, the cell apoptosis was increased, the expression of GRP78, ATF6, Bax protein expression and Bax/Bcl-2 were remarkably up-regulated (P < 0.05), but Bcl-2 protein expression was remarkably down-regulated in H/R group. Compared with the H/R group, the cell apoptosis decreased; the expression of GRP78, ATF6 , Bax and Bax/Bcl-2 were down-regulated (P < 0.05), but Bcl-2 was up-regulated in the groups with naringin three groups,especially naringin 20 and 40μg/mL groups had remarkably effect.Conclusion:The pretreatment of naringin can reduce the apoptosis of myocardial cell. The mechanism may be related to the inhibition of the apoptotic pathway of endoplasmic reticulum stress.

Key words: Naringin, GRP78, ATF6, Hypoxia-Reoxygenation injury , apoptosis, Bax/Bcl-2