Stereoselective block of a human cardiac potassium channel (Kv1.5) by bupivacaine enantiomers.
Stereoselective block of a human cardiac potassium channel (Kv1.5) by bupivacaine enantiomers.
复制标题
布比卡因对映体立体选择性阻断人心脏钾通道 (Kv1.5)。
DOI：
10.1016/s0006-3495(95)79914-3
复制
发表时间：
1995
影响因子：
3.4
通讯作者：
Snyders,DJ
中科院分区：
文献类型：
--
作者：
Valenzuela,C;Delpon,E;Tamkun,MM;Tamargo,J;Snyders,DJ
立体选择性药物通道相互作用可能有助于阐明局部麻醉药物阻断电压门控钾通道的分子基础。我们研究了布比卡因对映体对克隆的人心脏钾通道（hKv1.5）的作用。该通道在小鼠Ltk细胞系中稳定表达，并使用膜片钳技术的全细胞配置进行研究。这两种对映体修改的时间过程中，这种延迟整流电流。暴露于20 μ M的S（-）-布比卡因或R（+）-布比卡因均未改变电流的激活时间常数，但降低了峰值外向电流，并诱导随后的电流指数下降，时间常数分别为18.7 +/- 1.1和10.0 +/- 0.9 ms。S（-）-和R（+）-布比卡因的稳态阻滞水平（用250 ms去极化脉冲至+60 mV评估）平均分别为30.8 +/- 2.5%（n = 6）和79.5 +/- 3.2%（n = 6）（p < 0.001）。hKv1.5抑制的浓度依赖性显示S（-）-布比卡因和R（+）-布比卡因的表观KD值分别为27.3 +/-2.8和4.1 +/-0.7 microM，希尔系数接近1，表明每个通道结合一个对映体分子足以阻断钾渗透。结合速率常数（k）和解离速率常数（l）的分析得出l的值相似（S（-）-和R（+）-布比卡因分别为24.9 s-1和23.6 s-1），但结合速率常数不同（S（-）-和R（+）-布比卡因分别为1.0 x 10（6）M-1 s-1和4.7 x 10（6）M-1 s-1）。由任一对映体诱导的阻断在正至0 mV的电压范围内显示出浅的电压依赖性，即，其中通道完全打开，与0.16 +/-0.01的等效电距离Δ一致。这表明，在结合位点，布比卡因的两种对映体经历了16%的所施加的跨膜电场，参考内表面。两种布比卡因对映异构体均将返回时记录的尾电流幅度降低至-40 mV，并相对于对照减慢其时程，导致“交叉”现象。（400字处删节）
Stereoselective drug-channel interactions may help to elucidate the molecular basis of voltage-gated potassium channel block by local anesthetic drugs. We studied the effects of the enantiomers of bupivacaine on a cloned human cardiac potassium channel (hKv1.5). This channel was stably expressed in a mouse Ltk- cell line and studied using the whole-cell configuration of the patch-clamp technique. Both enantiomers modified the time course of this delayed rectifier current. Exposure to 20 microM of either S(-)-bupivacaine or R(+)-bupivacaine did not modify the activation time constant of the current, but reduced the peak outward current and induced a subsequent exponential decline of current with time constants of 18.7 +/- 1.1 and 10.0 +/- 0.9 ms, respectively. Steady-state levels of block (assessed with 250-ms depolarizing pulses to +60 mV) averaged 30.8 +/- 2.5% (n = 6) and 79.5 +/- 3.2% (n = 6) (p < 0.001), for S(-)- and R(+)-bupivacaine, respectively. The concentration dependence of hKv1.5 inhibition revealed apparent KD values of 27.3 +/- 2.8 and 4.1 +/- 0.7 microM for S(-)-bupivacaine and R(+)-bupivacaine, respectively, with Hill coefficients close to unity, suggesting that binding of one enantiomer molecule per channel was sufficient to block potassium permeation. Analysis of the rate constants of association (k) and dissociation (l) yielded similar values for l (24.9 s-1 vs. 23.6 s-1 for S(-)- and R(+)-bupivacaine, respectively) but different association rate constants (1.0 x 10(6) vs. 4.7 x 10(6) M-1 s-1 for S(-)- and R(+)-bupivacaine, respectively). Block induced by either enantiomer displayed a shallow voltage dependence in the voltage range positive to 0 mV, i.e., where the channel is fully open, consistent with an equivalent electrical distance delta of 0.16 +/- 0.01. This suggested that at the binding site, both enantiomers of bupivacaine experienced 16% of the applied transmembrane electrical field, referenced to the inner surface. Both bupivacaine enantiomers reduced the tail current amplitude recorded on return to -40 mV and slowed their time course relative to control, resulting in a "crossover" phenomenon.(ABSTRACT TRUNCATED AT 400 WORDS)