链霉素对增加豚鼠左心室后负荷所致单相动作电位变化的影响

Effect of streptomycin on monophasic action potential changes induced by increased left ventricular afterload in Guinea-pig hearts

目的 观察链霉素对左心室后负荷增加引起的在体豚鼠心肌单相动作电位变化的影响 ,评价牵张激活离子通道 (stretch -activatedchannels,SACs)在机械电反馈 (mechanoelectricalfeedback ,MEF)中的作用。方法 记录在体豚鼠左心室前中壁单相动作电位 (monophasicactionpotential,MAP)的过程中结扎其升主动脉 5s ,间隔 5min重复一次 ,在重复之前由颈静脉注射链霉素 (2 0mg/kg) ,测量结扎升主动脉前后单相动作电位 5 0 %和 90 %复极时程 (APD50 和APD90 )。结果 应用链霉素之前 ,短时间结扎升主动脉 ,左心室后负荷由 (30± 8)mmHg增加到(71± 1 9)mmHg(P <0 0 5 ) ,相应地 ,伴随左心室后负荷的增加 ,APD50 由 (76± 1 2 )ms缩短为 (6 7± 1 3)ms(P <0 0 5 ) ,同时 ,APD90 由 (1 2 0± 1 7)ms缩短为 (1 1 5± 1 6 )ms(P <0 0 5 ) ;应用链霉素之后 ,短时结扎升主动脉可引起左心室后负荷相似的变化 ,但APD50 和APD90 没有发生明显变化。结论 左心室后负荷增加引起在体豚鼠心肌APD50 和APD90缩短 ,链霉素可抑制此效应 。

Objective To study the effect of streptomycin on monophasic action potential changes induced by increased left ventricular afterload in Guinea-pig hearts and to evaluate whether stretch-activated channels (SACs) had an effect on mechanoelectrical feedback. Methods When the monophasic action potentials of the midanterior left ventricular wall of Guinea-pig hearts were recorded, the ascending aorta was clamped for 5 s. At 5 min interval, second clamping of the ascending aorta was carried out after streptomycin (20 mg/kg ) was injected into the heart through cervical vein cannula. Monophasic action potential duration at 50% and 90% (APD 50 and APD 90 ) before and after clamping of the ascending aorta were measured. Results Before administration of streptomycin, the left ventricular afterload increased from (30±8)mmHg to (71±19)mmHg during transient ascending aorta occlusion( P <0 05). Accordingly APD 50 decreased from (76±12)ms to (67±13)ms( P <0 05) and APD 90 decreased from (120±17)ms to (115±16)ms( P <0 05). After administration of streptomycin, similar change in left ventricular afterload was founded. However, APD 50 and APD 90 did not change significantly. Conclusion A decrease in APD 50 and APD 90 induced by elevation of left ventricular afterload was founded in this study and streptomycin had an inhibitory effect on it, suggesting that SACs might be involved in this process.