三磷酸腺苷敏感性钾通道开放剂对模拟缺血/再灌注乳鼠窦房结细胞内钙及L-型钙电流的影响

通过观察三磷酸腺苷敏感性钾通道(KATP)开放剂对模拟缺血/再灌注(I/R)时乳鼠窦房结细胞内Ca2+及ICaL的影响,探讨模拟缺血预适应(IP)对模拟I/R时窦房结细胞的保护机制。取培养2天的乳鼠窦房结细胞,随机分为①对照组;②模拟I/R组;③模拟IP组;④Diazoxide(线粒体KATP开放剂)+模拟I/R组;⑤5HD(线粒体KATP阻断剂)+模拟IP组。以免疫荧光技术标记细胞内Ca2+,通过激光共聚焦显微镜检测荧光强度变化;以全细胞膜片钳技术检测ICaL。结果:①Diazoxide预处理能模拟IP效应,显著降低I/R后窦房结细胞内Ca2+荧光强度(P<0.01),增加相应电压下的ICaL电流密度,使电流电压曲线相对下移。②5HD预处理阻断了IP效应,其窦房结细胞内Ca2+荧光强度及ICaL电流密度与I/R组接近。结论:KATP开放剂预处理能模拟IP效应,减轻模拟I/R引起的窦房结细胞内Ca2+超载,改善受抑的ICaL。

Comparison of Effects of ATP-sensitive Potassium Channel Opener Pretreatment and Mimic Ischemic Preconditioning on [Ca2+]i and L-type Calcium Current of Sinoatrial Node Cells of Neonatal Rat

To compare the effects of mimic ischemic preconditioning(IP) and the pretreatment of ATP-sensitive potassium (K_ ATP) channel opener on [Ca 2+]_i and I_ Ca-L ,sinoatrial node cells were randomized to five groups: ①Control,②Ischemia/reperfusion(I/R),③IP,and ④Diazoxide(mitochondrial K_ ATP channel opener )+I/R, ⑤5-HD(mitochondrial K_ ATP channel blocker)+IP. After labeled with fura 4, Fluorescence intensity of [Ca 2+]_i was studied with laser confocal microscopy and I_ Ca-L was recorded by whole-cell patch clamp technology. Results:① Both Diazoxide pretreatment and IP significantly reduced the fluorescence intensity of [Ca 2+]_i ,enhanced I_ Ca-L compared with I/R(P<0.01),and shifted the I-V curve to more negative value.②5-HD pretreatment blocked the effects of IP completely(P<0.01). Conclusion: K_ ATP channel opener can mimic the effects of IP′s reducing the overload of [Ca 2+]_i caused by I/R and increasing I_ Ca-L weakened by I/R.