Yu S P, Kerchner G A
Department of Neurology, Center for the Study of Nervous System Injury, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Neurosci Res. 1998 Jun 1;52(5):612-7. doi: 10.1002/(SICI)1097-4547(19980601)52:5<612::AID-JNR13>3.0.CO;2-3.
Endogenous voltage-gated potassium currents were investigated in human embryonic kidney (HEK293) and Chinese hamster ovary (CHO) cells using whole-cell voltage clamp recording. Depolarizing voltage steps from -70 mV triggered an outwardly rectified current in nontransfected HEK293 cells. This current had an amplitude of 296 pA at +40 mV and a current density of 19.2 pA/pF. The outward current was eliminated by replacing internal K+ with Cs+ and suppressed by the K+ channel blockers tetraethylammonium and 4-aminopyridine. Raising external K+ attenuated the outward current and shifted the reversal potential towards positive potentials as predicted by the Nernst equation. The current had a fast activation phase but inactivated slowly. These features implicate delayed rectifier (I(K))-like channels as mediators of the observed current, which was comparable in size to I(K) currents in many other cells. A small native inward rectifier current but no transient outward current I(A), the M current I(M), or Ca2+-dependent K+ currents were detected in HEK293 cells. In contrast to these findings in HEK293 cells, little or no I(K)-like current was detected in CHO cells. The difference in endogenous voltage-activated currents in HEK293 and CHO cells suggest that CHO cell lines are a preferred system for exogenous K+ channel expression.
利用全细胞膜片钳记录技术，对人胚肾（HEK293）细胞和中国仓鼠卵巢（CHO）细胞中的内源性电压门控钾电流进行了研究。在未转染的HEK293细胞中，从-70 mV的去极化电压阶跃引发了外向整流电流。该电流在+40 mV时的幅度为296 pA，电流密度为19.2 pA/pF。通过用Cs+取代内部K+消除外向电流，并用K+通道阻滞剂四乙铵和4-氨基吡啶抑制该电流。如能斯特方程所预测，提高外部K+可减弱外向电流，并使反转电位向正电位移动。该电流具有快速激活相，但失活缓慢。这些特征表明延迟整流（I(K)）样通道是所观察到电流的介质，其大小与许多其他细胞中的I(K)电流相当。在HEK293细胞中检测到小的内向整流电流，但未检测到瞬时外向电流I(A)、M电流I(M)或Ca2+依赖性K+电流。与HEK293细胞中的这些发现相反，在CHO细胞中几乎未检测到或未检测到I(K)样电流。HEK293细胞和CHO细胞中内源性电压激活电流的差异表明，CHO细胞系是外源K+通道表达的首选系统。
