蛋白激酶A抑制剂H-89的致心律失常效应及机制

The proarrhythmic effect and mechanism of PKA antagonist H-89

目的观察蛋白激酶A（PKA）抑制剂H-89对大鼠心律和心肌细胞膜内向整流钾电流（Ik1）、钠钙交换体电流（INa/Ca）的影响，从而评估其药理学应用价值。方法成年sD大鼠麻醉后开胸取出心脏行Langendofff主动脉逆行灌流，记录心电图，观察-89给药20min内对离体心脏节律的影响。应用全细胞膜片钳技术观察H-89对胶原酶分解的大鼠心室肌细胞膜Ik1和INa/Ca的影响。结果1～10μmol／LH-89可在大鼠离体心脏诱发明显的心律失常，室性期前收缩（PVB）数目，室速（VT）、室颤（VF）持续时间和发生率呈浓度依赖性增高（P〈O．05）。膜片钳记录结果显示，H-89可浓度依赖性抑制I。（P〈0．05），在5μmol／L时即可完全阻断Ik1类似于0．5mmol／L氯化钡（BaCl2）的效应。但H-89（1-10μmol／L）对INa/Ca无明显作用（P〉O．05）。结论H-89对心肌细胞膜电流的异常扰动是其致心律失常风险的主要电生理．机制，可由PKA依赖性或非PKA依赖性药理学作用共同介导。

Objective To observe the effect of N-（2-p-bromo-cinnamylaminoethyl）-5-isoquinoline- sulfonamide （H-89）, a potent and potentially selective inhibitor of Protein Kinase A （PKA）, on rat heart rhythm and cardiac inward rectifier K＋ current （IK1）, Na＋-Ca2＋ exchanger current （INa/Ca）. Methods Langendorff-perfused SD rat hearts were subjected to H-89 at 1-10μmol/L respectively for 20 minutes. The ECGs were recorded si- multaneously. Whole-cell patch clamp technique was used to investigate the effects of H-89 on cardiac IKI and INa/Ca in enzymatic dissociated rat ventricular myocytes. Results ＇H-89 at 1-10 μmol/L displayed singnificant proar- rhythmic risk in ex vivo hearts, the total of PVB, the incidence and duration of VT and VF were increased con- centration-dependently（P〈0.05 ）. Patch-clamp data showed H-89 at 1-10 μmol/L had no effect on Ik1 CP〉0.05 ） while inhibited IK1 in a concentration dependent manner（P〈0.05 ）. At 5 μmol/L, H-89 completely blocked IK1（P〈 0.05） just as the action of 0.5 mmol/L BaC12. Conclusion The underlying mechanism of proarrhythmic risk of H- 89 is ascribed to the disturbance of membrane ion currents mediated by both PKA-dependent and PKA-indepen- dent pathway.