模拟缺血-再灌注对窦房结细胞自发性动作电位的影响及吡那地尔的干预作用

目的:探讨模拟缺血-再灌注对窦房结细胞动作电位的影响及K_ATP通道开放剂的干预效果。方法:取培养2d的乳鼠窦房结细胞进行实验,随机分为对照组、模拟缺血-再灌注组(I/R)、K_ATP通道开放剂pinacidil干预组(P+I/R)及K_ATP通道阻断剂5-HD干预组(5-HD+P+I/R及5-HD+I/R)。采用全细胞膜片钳技术记录窦房结细胞动作电位,测定最大舒张电位(MDP)、0期去极化速度(UV)、超射值(APO)、动作电位周期(IBI)及50%复极时程(APD₅₀)的变化。结果:①I/R组MDP(-55.2±4.5)mV明显低于对照组(P＜0.05),APD₅₀(64.3±3.8)ms明显短于对照组(P＜0.01),而UV(3.8±0.5)V/s及APO(14.2±2.0)mV则明显小于对照组(P＜0.01),但IBI无明显改变。②P+I/R组的MDP及APO明显大于I/R组,IBI明显长于、UV显著快于I/R组,但APD₅₀进一步缩短。③5-HD不能阻断pinacidil对模拟缺血-再灌注窦房结细胞MDP、IBI和APD₅₀的影响,但能使pinacidil引起的UV及APO改变发生逆转。结论:Pinacidil可能通过开放不同种类K_ATP通道对模拟缺血-再灌注窦房结细胞动作电位产生影响。

Effects of simulated ischemia/reperfusion on spontaneous action potentials in primary cultured sinoatrial node cells and the influence of pinacidil

AIM: To study the effects of ischemia/reperfusion (I/R) on primary cultured sinoatrial node (SAN) cells and the influence of pinacidil (a K_(ATP) channel activator). METHODS: The SAN cells were isolated from newborn rats and purified. The 48 h cultured cells were cultivated in following mediums: simulated reperfusion solution as normal control, simulated ischemia/reperfusion solution (I/R), Pinacidil I/R (P I/R), 5-HD P I/R and 5-HD I/R. Spontaneous action potentials were recorded by ruptured-patch whole-cell technique in current clamp ((I=0)) and the maximum diastolic potential (MDP), upstroke velocity (UV), action potential overshoot (APO), interbeat interval (IBI) and action potential durations at 50% repolarization (APD_(50)) were measured. RESULTS: Compared with control group, simulated ischemia/reperfusion shorten APD_(50), reduced UV, MDP and APO. Exposed to pinacidil, MDP of cells in I/R groups was hyperpolarized; IBI, UV and APO were increased; APD_(50) was shorten. 5-HD couldn't block the effects of pinacdil on APD_(50), IBI and MDP, but reversed its actions on increasing UV and APO. CONCLUSIONS: Pinacidil made changes of AP in I/R group by opening different K_(ATP) channels of SAN cells. The role of this changes on protection in SAN cells during ischemia/reperfusion requires further investigation.