Effects of β2-Adrenergic Antagonist on Cytosolic Ca^2＋ in Ventricular Myocytes from Infarcted Rat Heart

Objectives To investigate the effects ofβ2-adrenergic antagonist on cytosolic Ca2 (Ca2 ]i) in ventricular myocytes from infarcted rat heart. Methods A ligature was placed around left anterior descending coronary artery of rat hearts. Rats in the control group were sham-operated. Cardiomyocytes were dissociated at two, four, eight weeks after myocardial infarction (MI) and Ca2 ]i was measured via fura-2 fluorescence. The response of cardiomyocytes to isoproterenol in presence or absence of betal-adrenergic antagonist atenolol, beta2-adrenergic antagonist ICI118, 551 or non-selectiveβ1, 2- adrenergic antagonists propranolol was examined. Results The followings were found that ICI118, 551 had no significant effects on the rise of Ca2 ]i induced by isoproterenol in normal ventricular myocytes (P > 0.05 ), ICI118, 551 only significantly attenuated the rise of Ca2 ]i induced by isoproterenol at four weeks and eight weeks after MI (24.5%±5.7% vs 57.8%±13.2%, P<0.01; 12.2%±7.9% vs 44.6%±11.3%, P< 0.01). Atenolol had suppressive effects only in the control group and the post-Mi group of two weeks (P< 0.05 ) , and propranolol had suppressive effects in the control and all the three post-Mi groups (P < 0.01). Conclusions Beta2-adrenergic antagonist ICI118, 551 may exert negative effects on Ca2 overload initiated by sympathetic stimulation after MI.