Thierfelder S, Hirche H, Benndorf K
Institut für Vegetative Physiologie, Universität zu Köln, Germany.
Pflugers Arch. 1994 Jul;427(5-6):547-9. doi: 10.1007/BF00374273.
Transient K+ outward currents (Ito) were measured in enzymatically isolated ventricular mouse heart cells with a patch clamp technique in the whole cell configuration. Exposure of the cells to substrate-free anoxia gradually decreased both the peak and the late Ito. The inactivation time course of Ito was fitted with two exponentials. After 4-10 min of anoxia, the contribution of the fast and slow exponential decreased to 60 +/- 7% and 62 +/- 4% of the control value and recovered after reoxygenation within 1-3 min to 84 +/- 5% and 75 +/- 6% (n = 10; all mean +/- SEM), respectively. The time constants of the exponentials were invariant to anoxia. Voltage dependence of activation and inactivation of Ito were not influenced by anoxia. Application of stimulators of protein kinase A and C, cGMP- dependent protein kinase, or of the oxidant diamide during anoxia did not recover Ito. It is concluded that under conditions of metabolic stress, Ito is reversibly down-regulated leaving inactivation kinetics unchanged. The underlying mechanism is as yet unknown but does neither involve a decreased activity of protein kinase A, protein kinase C, nor c-GMP dependent protein kinase.
采用膜片钳技术在全细胞模式下，对酶分离的小鼠心室肌细胞中的瞬时钾外向电流（Ito）进行了测量。将细胞暴露于无底物的缺氧环境中，Ito的峰值和晚期电流均逐渐降低。Ito的失活时间过程拟合为两个指数函数。缺氧4 - 10分钟后，快速和慢速指数函数的贡献分别降至对照值的60±7%和62±4%，复氧后1 - 3分钟内分别恢复至84±5%和75±6%（n = 10；所有数据均为平均值±标准误）。指数函数的时间常数不受缺氧影响。Ito的激活和失活电压依赖性不受缺氧影响。在缺氧期间应用蛋白激酶A、蛋白激酶C、cGMP依赖性蛋白激酶的刺激剂或氧化剂二酰胺，均不能恢复Ito。得出的结论是，在代谢应激条件下，Ito可逆性下调，而失活动力学不变。其潜在机制尚不清楚，但既不涉及蛋白激酶A、蛋白激酶C活性降低，也不涉及cGMP依赖性蛋白激酶活性降低。
