Pancrazio J J, Viglione M P, Tabbara I A, Kim Y I
Department of Biomedical Engineering, University of Virginia Health Sciences Center, Charlottesville 22908.
Cancer Res. 1989 Nov 1;49(21):5901-6.
Small-cell carcinoma of the lung is a highly lethal form of cancer associated with a wide variety of paraneoplastic syndromes. Using the patch-clamp technique, we have directly demonstrated the presence of voltage-gated K+, Na+, and Ca2+ channels in three cell lines of human small-cell carcinoma, NCI-H128, NCI-H69, and NCI-H146. Whole-cell currents were measured from the tumor cells held at -80 mV and depolarized to -60 to +120 mV. Outward K+ current (IK), which was found in every cell tested, reached 1.58 +/- 0.12 nA (mean +/- SE, n = 24 cells) for H128 cells and 2.14 +/- 0.18 nA (n = 41) for H69 cells in response to a test potential of +80 mV. Unlike H69 and H128 tumor cells, IK from H146 cells occasionally exhibited partial inactivation during the 60-ms pulse length and reached 0.94 +/- 0.15 nA (n = 18) in response to a +80 mV test potential. IK from each of the cell lines was significantly reduced by 4-aminopyridine and tetraethylammonium. The rapidly inactivating inward Na+ current (INa), recorded in H146 cells and about 30% of the H69 and H128 cells tested, demonstrated a peak amplitude of 58 +/- 6 pA (n = 11) at 0 mV and a reversal potential of 47 +/- 2 mV (n = 11). Externally applied tetrodotoxin quickly suppressed INa. For the H128 and H69 tumor cells, inward Ca2+ current (ICa), observed in about 25% of the cells exposed to 10 mM [Ca2+]o, peaked at 5.1 +/- 0.4 ms (n = 5) with an amplitude of 46 +/- 14 pA (n = 5) at +20 mV and partially inactivated over the 40-ms depolarization. In H128 cells exposed to isotonic Ba2+ (110 mM), inward currents with time courses similar to those of ICa were recorded. Nearly all H146 tumor cells demonstrated a significant inward Ca2+ current which peaked with an amplitude of 93 +/- 16 pA (n = 26) at +30 to +40 mV in the presence of 10 mM [Ca2+]o. Application of test potentials 2 s in duration revealed that H146 ICa inactivated in a voltage-dependent manner with a time constant on the order of seconds. Adjustment of the holding potential from -80 mV to -40 mV had no observable effect on the amplitude of the evoked current. These voltage-dependent ion channels may have integral roles in several small-cell carcinoma bioelectric phenomena, including secretion, resting membrane potential, and action potential generation.(ABSTRACT TRUNCATED AT 400 WORDS)
肺小细胞癌是一种极具致死性的癌症形式，与多种副肿瘤综合征相关。我们使用膜片钳技术，直接证实了在人小细胞癌的三种细胞系NCI-H128、NCI-H69和NCI-H146中存在电压门控的钾离子（K⁺）、钠离子（Na⁺）和钙离子（Ca²⁺）通道。从保持在-80 mV并去极化至-60到+120 mV的肿瘤细胞中测量全细胞电流。在每个测试细胞中均发现的外向K⁺电流（IK），在+80 mV测试电位下，H128细胞达到1.58±0.12 nA（平均值±标准误，n = 24个细胞），H69细胞达到2.14±0.18 nA（n = 41）。与H69和H128肿瘤细胞不同，H146细胞的IK在60毫秒脉冲长度期间偶尔会出现部分失活，在+80 mV测试电位下达到0.94±0.15 nA（n = 18）。每个细胞系的IK均被4-氨基吡啶和四乙铵显著降低。在H146细胞以及约30%测试的H69和H128细胞中记录到快速失活的内向Na⁺电流（INa），在0 mV时峰值幅度为58±6 pA（n = 11），反转电位为47±2 mV（n = 11）。外部施加的河豚毒素迅速抑制INa。对于H128和H69肿瘤细胞，在约25%暴露于10 mM细胞外钙离子浓度（[Ca²⁺]o）的细胞中观察到内向Ca²⁺电流（ICa），在+20 mV时于5.1±0.4毫秒达到峰值，幅度为46±14 pA（n = 5），并在40毫秒去极化过程中部分失活。在暴露于等渗钡离子（110 mM）的H128细胞中，记录到时间进程与ICa相似的内向电流。几乎所有H146肿瘤细胞均表现出显著的内向Ca²⁺电流，在10 mM [Ca²⁺]o存在下，在+30至+40 mV时峰值幅度为93±16 pA（n = 26）。施加持续2秒的测试电位显示，H146的ICa以电压依赖性方式失活，时间常数约为秒级。将钳制电位从-80 mV调整至-40 mV对诱发电流的幅度没有可观察到的影响。这些电压依赖性离子通道可能在几种小细胞癌生物电现象中发挥重要作用，包括分泌、静息膜电位和动作电位的产生。（摘要截取自400字）
