AIM:To investigate the protective effect of losartan(Los) on apoptosis of H9c2 cells induced by isoprenaline(ISO),and to discover its related mechanism.METHODS:H9c2 cells cultured on plastic plates were divided into control,ISO,ISO+Los,ISO+Los+LY294002 and DMSO groups.Cell apoptosis was evaluated by flow cytometery and agarose gel electrophoresis.The mRNA levels of bax,bcl-2 and caspase-9 were detected by RT-PCR and the expressions of phosphorylated and total Akt(p-Akt and t-Akt) were assessed by Western blotting.The cAMP was measured by radioimmunoassay.RESULTS:ISO at concentration of 10 ?mol/L induced apoptosis of H9c2 with an increase in bax/bcl-2,caspase-9 and cAMP.Addition of 10 ?mol/L losartan inhibited apoptosis obviously with a decrease in bax/bcl-2,caspase-9 and cAMP.A significant increase in p-Akt was observed,and its protein level was elevated.LY294002 at concentration of 1 ?mol/L abolished the protective effects of losartan on ISO-induced apoptosis in H9c2 cells.CONCLUSION:ISO might induce H9c2 cell apoptosis through stimulation of ?-adrenergic receptor(?-AR).Los inhibits downstream signaling of ?-AR,and promotes the activation of Akt.Subsequently it might attenuate the apoptosis induced by ?-adrenergic stimulation of ISO.