MODIFICATION OF THE TRANSIENT OUTWARD CURRENT OF RAT ATRIAL MYOCYTES BY METABOLIC INHIBITION AND OXIDANT STRESS
MODIFICATION OF THE TRANSIENT OUTWARD CURRENT OF RAT ATRIAL MYOCYTES BY METABOLIC INHIBITION AND OXIDANT STRESS
复制标题
DOI：
10.1113/jphysiol.1993.sp019863
复制
发表时间：
1993-10-01
影响因子：
5.5
通讯作者：
ROBERTS, ML
中科院分区：
文献类型：
--
作者：
PIKE, GK;BRETAG, AH;ROBERTS, ML
1.心肌细胞中瞬时外向电流（I（TO））的一个假定功能是调节动作电位的形状，从而调节心肌收缩力。此外，有人认为，这种电流可能有助于防止心脏缺血期间的心律失常。在我们对I（TO）可能的抗肿瘤作用的研究中，我们检测了它对代谢抑制和氧化应激的反应。使用标准膜片钳技术从大鼠心房肌细胞获得全细胞记录。抑制代谢，使用10毫米2-脱氧-D-葡萄糖（2-DG），以阻止糖酵解与或不添加2毫米氰化物，以阻止氧化磷酸化，导致抑制I（TO）在-70 mV的保持电位。将保持电位移至-80 mV可恢复-I（TO），表明代谢抑制使I（TO）的失活曲线向负方向移动.准稳态失活曲线显示，在I（TO）失活诱导的2-DG和氰化物的完全代谢抑制的转变。在观察到偏移后不久，肌细胞通常收缩。在钌红的存在下，收缩延迟，心肌细胞可以经历几次暴露于代谢抑制剂，每次显示I（TO）失活的转变。位移范围在-7和-20 mV之间。使用双脉冲方案测定灭活的回收率。在代谢抑制期间，在-80 mV的保持电位下的恢复时间常数可逆地从48 +/- 8变为129 +/- 21 ms（n = 4）。在代谢抑制过程中，I（TO）从-100 mV的保持电位向负方向移动，从0.3 +/- 3-0的半激活电压变为-14.7 +/- 2.5 mV（n = 5）。这种-15 mV的偏移使I（TO）的振幅在0 mV时增加约30%。6.当肌细胞受到1 mm叔丁基过氧化氢（TBHP）或100 nM虎红光活化诱导的氧化应激时，可显示I（TO）失活的变化与代谢抑制产生的变化相似。此外，从20到200 nm的游离Ca 2+的移液管浓度的增加也使I（TO）失活向负方向移动。这些结果提出了一种可能性，即在代谢抑制和氧化应激过程中发生的细胞内[Ca 2 +]的升高改变了I（TO）的激活和失活。这种对胞质Ca 2+的敏感性可能会影响正常心脏动作电位期间的I（TO），以及在[Ca 2 +]i升高的异常条件下。失活转移引起的I（TO）降低将导致平台电位升高和动作电位增宽。
1. A putative function of the transient outward current (I(TO)) in cardiac myocytes is to modulate the shape of the action potential and, consequently, cardiac contractility. In addition, it has been suggested that this current may help protect against arrhythmias during periods of cardiac ischaemia. In our investigation of the possible anti-arrhythmic action of I(TO), we have examined its response to metabolic inhibition and oxidant stress.2. Whole-cell recordings were obtained from rat atrial myocytes using standard patch-clamp techniques. Inhibition of metabolism, using 10 mm 2-deoxy-D-glucose (2-DG) to block glycolysis with or without the addition of 2 mm cyanide to block oxidative phosphorylation, led to inhibition of I(TO) at a holding potential of - 70 mV. Shifting the holding potential to - 80 mV restored -I(TO), suggesting that metabolic inhibition had shifted the inactivation curve of I(TO) in a negative direction.3. Quasi steady-state inactivation curves revealed a shift in I(TO) inactivation induced by complete metabolic inhibition with 2-DG and cyanide. Myocytes typically contracted shortly after the shift was observed. In the presence of Ruthenium Red, contraction was delayed and myocytes could undergo several exposures to the metabolic inhibitors, each time displaying a shift in I(TO) inactivation. The shifts ranged between - 7 and - 20 mV.4. Recovery from inactivation was determined using a two-pulse protocol. The time constant of recovery at a holding potential of - 80 mV reversibly shifted from 48 +/- 8 to 129 +/- 21 ms during metabolic inhibition (n = 4).5. The activation of I(TO) from a holding potential of - 100 mV shifted in a negative direction during metabolic inhibition, from a half-activation voltage of 0.3 +/- 3-0 to - 14.7 +/- 2.5 mV (n = 5). Such a - 15 mV shift increases the amplitude of I(TO) by approximately 30 % at 0 mV.6. A shift in I(TO) inactivation similar to that produced by metabolic inhibition could be shown when myocytes were subjected to oxidant stress induced by either 1 mm t-butyl hydroperoxide (TBHP) or the photoactivation of 100 nM Rose Bengal. Furthermore, an increase in pipette concentration of free Ca2+ from 20 to 200 nm also shifted I(TO) inactivation in a negative direction.7. These results raise the possibility that the rise in intracellular [Ca2+] occurring during both metabolic inhibition and oxidant stress modifies activation and inactivation of I(TO). Such a sensitivity to cytosolic Ca2+ may influence I(TO) during the action potential in the normal heart as well as under abnormal conditions where [Ca2+]i rises. The depression of I(TO) resulting from the shift in inactivation would lead to an elevation of the plateau potential and widening of the action potential.