链霉素对兔左心室后负荷增加所致电生理变化的影响

Effect of streptomycin on electrophysiological changes caused by rising of left ventricular afterload in rabbits

目的 :探讨左心室后负荷增加引起的心脏电生理变化及链霉素和维拉帕米对其的影响。方法 :采用部分夹闭家兔升主动脉根部以增加左室后负荷的在体心脏模型 ,观察后负荷增加前后心肌相对不应期 (RRP)、有效不应期 (ERP)、单相动作电位时程 (MAPD90 )和室颤阈 (VFT)的变化 ,并比较了链霉素和维拉帕米对这些电生理参数变化的影响。结果 :后负荷上升 [(72± 11)mmHg]引起RRP、ERP和MAPD90 缩短 ,VFT下降 (P <0 .0 1) ;链霉素可有效抑制后负荷增加引起的心脏电生理变化 ;而维拉帕米除可提高VFT外 (P <0 0 1) ,对后负荷增加引起RRP、ERP和MAPD90的缩短没有明显影响 (P >0 0 5 )。结论 :结果提示牵张激活性离子通道的活化可能参与后负荷增加引起的心脏电生理变化过程 ,且链霉素通过抑制这种离子通道的活化而发挥作用。

AIM: The aim of this study was to study the changes of rabbit heart electrophysiological properties caused by increasing left ventricular afterload, and to assess the effects of streptomycin or verapamil on these changes. METHODS: The rabbit heart preparation in situ was used,and the afterload of left ventricle was increased by clipping in part the root of ascending aorta. The changes of heart electrophysiological parameters including relative refractory period (RRP),effective refractory period (ERP),monophasic action potential duration (MAPD_ 90 ) and ventricular fibrillation threshold(VFT) were observed before and after altering the afterload of left ventricle and were compared in the absence and presence of streptomycin or verapamil. RESULTS: The rising of left ventricular afterload [(72±11)mmHg] led to shortening of RRP,ERP and MAPD_ 90 ,and to descent of VFT ( P< 0.01). Streptomycin inhibited these changes of heart electrophysiological parameters caused by elevation of left ventricular afterload. In contrast,verapamil had no effects on the afterload-related changes of RRP, ERP and MAPD_ 90 ( P> 0.05) except increasing of VFT ( P< 0.01). CONCLUSION: The electrophysilogical effect of streptomycin appears consistent with inhibition of stretch-activated ion channels,suggesting that the stretch-activated ion channels might be involved in the afterload-related changes of heart electrophysiological properties.