Cui Y, Terrar D A
University Department of Pharmacology, Oxford, England.
J Cardiovasc Pharmacol. 1995 May;25(5):691-5. doi: 10.1097/00005344-199505000-00002.
We investigated effects of caffeine on inward rectifier potassium current (Ik1) in voltage-clamped ventricular cells by slow ramp depolarization (15 mV/s). Caffeine 10 mM applied in the solution bathing the cells consistently reduced the slope of the current-voltage (I-V) relation over the range of -80 to -40 mV. This effect of caffeine was not prevented by loading cells with BAPTA (1,2-bis(2-aminophenoxy) ethane N,N,N',N'-tetra-acetic acid) to suppress contraction. In the absence of caffeine, reducing extracellular potassium from 5.4 to 2.7 mM caused the expected shift of the reversal potential for current in the negative direction and increased rectification. In low potassium, 10 mM caffeine continued to reduce the slope of the I-V relation. When 2 mM barium was applied to suppress Ik1, any effects of 10 mM caffeine were slight or absent. The observations are consistent with a blocking action of caffeine on Ik1 in guinea pig ventricular myocytes.
我们通过慢斜坡去极化（15 mV/s）研究了咖啡因对电压钳制心室细胞内向整流钾电流（Ik1）的影响。将10 mM咖啡因应用于灌流细胞的溶液中，在-80至-40 mV范围内持续降低电流-电压（I-V）关系的斜率。用BAPTA（1,2-双（2-氨基苯氧基）乙烷N,N,N',N'-四乙酸）加载细胞以抑制收缩并不能阻止咖啡因的这种作用。在不存在咖啡因的情况下，将细胞外钾从5.4 mM降至2.7 mM会导致电流反转电位按预期向负方向移动并增加整流。在低钾情况下，10 mM咖啡因继续降低I-V关系的斜率。当应用2 mM钡来抑制Ik1时，10 mM咖啡因的任何作用都很轻微或不存在。这些观察结果与咖啡因对豚鼠心室肌细胞中Ik1的阻断作用一致。
