广枣总黄酮对大鼠心室肌细胞IC_a、I_(to)和细胞[Ca~(2+)]_i的影响

目的　观察广枣总黄酮对大鼠心室肌细胞L 型钙通道电流 (ICa)和瞬时外向钾通道电流 (Ito)以及对心肌细胞内游离钙浓度 (Ca2 + ]i)的影响 ,探讨其抗心律失常作用机制。方法　全细胞膜片钳记录大鼠心室肌细胞ICa、Ito,激光共聚焦显微镜观察细胞 Ca2 + ]i 的变化。结果　在钳制电压- 4 0mV ,实验电压 - 4 0～ +5 0mV时 ,广枣总黄酮 10 0mg·L-1对心室肌细胞ICa无显著影响 ;在钳制电压 - 6 0mV ,实验电压 - 4 0～ +5 0mV时显著抑制瞬时外向钾通道Ito(P <0 0 5 ) ;而激光共聚焦显微镜结果显示广枣总黄酮在 5 0、10 0、2 0 0mg·L-1却降低缺氧复氧心肌细胞收缩期和静息期Ca2 + ]i 的浓度。结论　广枣总黄酮对心肌细胞ICa无显著影响 ,可显著抑制瞬时外向钾通道Ito,并可明显降低心肌细胞收缩期和静息期细胞 Ca2 + ]i 浓度。这可能是其抗心律失常和保护缺血心肌的主要作用机制。

Effects of total flavones of choerospondias axillaris fructus on L-type Ca2+ current,transient outward K+ and intracellular free Ca2+ of ventricular myocytes in rats

Aim To study the effects of total flavones of choerospondias axiaris fructus (TFC) on L-type Ca 2+ current, transient outward K+ and intracellular free Ca of ventricular myocytes in rats and its mechanism of antiarrhythmia. Methods L-type Ca 2+ current and transient outward K+ were recorded by pach-clamp whole cell recording technique. Intracellular free Ca 2+ was measured by calcium fluorescent probe Fluo-3/AM and laser confocal microscope. Results L-type Ca 2+ current had not markedly changed by TFC 100 mg·L -1 at pach voltage -40 mV and experiment voltage -40～+50 mV. Ttransient outward K+ was markedly inhibited by TFC 100 mg·L -1 at pach voltage -60 mV and experiment voltage -40～+50 mV. Observations under laser confocal microscope indicated that Intracellular free Ca 2+ of resting phase and systole phase was decreased markedly by TFC 50, 100, 200 mg·L -1 in myocardia cells under ischemia and hypoxia condition. Conclusions TFC could markedly prolongate the action potential phase because of the reduction of transient outward K+, but TFC has no effecte on L-type Ca 2+ current. TFC also could markedly decrease intracellular free Ca 2+ of resting phase and systole phase in myocardia cells. The actions of antiarrhythmia and anti-myocardia-ischemia are concerned with the above mechanism of TFC.