Gérard V, Rouzaire-Dubois B, Dilda P, Dubois J M
Laboratoire de Neurobiologie cellulaire et moléculaire, CNRS, 91198 Gif-sur-Yvette Cedex, France.
J Exp Biol. 1998 Jan;201(Pt 1):21-31. doi: 10.1242/jeb.201.1.21.
A population of NG108-15 neuroblastoma cells resistant to doxorubicin (NG/DOXR) was established. The cells exhibited a multidrug resistance phenotype with cross-resistance to vinblastin and colchicine, overexpression of a 170 kDa membrane protein identified as P-glycoprotein and reversal of resistance by verapamil and quinine. Compared with NG108-15 cells, NG/DOXR cells showed an increase in Na+ current density and a decrease in cyclic-AMP-activated Cl- current density with no change in K+- and volume-sensitive Cl- current densities. As previously observed in NG108-15 cells, the vacuolar-type H+-ATPase inhibitors bafilomycin A1 and nitrate induced membrane depolarizations in NG/DOXR cells. The resting potentials of sensitive and resistant cells were not significantly different, but the depolarizations evoked by these agents were significantly larger in NG/DOXR than in NG108-15 cells. The resting membrane potential of NG/DOXR cells, but not that of NG108-15 cells, was depolarized by verapamil, and this effect was abolished by bafilomycin. The volume-sensitive Cl- currents of drug-sensitive and drug-resistant cells were inhibited by a decrease in intracellular pH from 7.3 to 6.8. Whereas bafilomycin prevents activation of Cl- currents in both drug-sensitive and drug-resistant cells, verapamil inhibited the Cl- current only in NG/DOXR cells. The results are discussed in terms of the roles of cytoplasmic pH and membrane potential in multidrug resistance.
建立了对阿霉素耐药的NG108 - 15神经母细胞瘤细胞群体（NG/DOXR）。这些细胞表现出多药耐药表型，对长春碱和秋水仙碱具有交叉耐药性，一种被鉴定为P - 糖蛋白的170 kDa膜蛋白过表达，并且维拉帕米和奎宁可逆转耐药性。与NG108 - 15细胞相比，NG/DOXR细胞的Na⁺电流密度增加，环磷酸腺苷激活的Cl⁻电流密度降低，而K⁺和容积敏感性Cl⁻电流密度没有变化。如先前在NG108 - 15细胞中观察到的那样，液泡型H⁺ - ATP酶抑制剂巴弗洛霉素A1和硝酸盐可诱导NG/DOXR细胞发生膜去极化。敏感细胞和耐药细胞的静息电位没有显著差异，但这些药物引起的去极化在NG/DOXR细胞中比在NG108 - 15细胞中显著更大。维拉帕米可使NG/DOXR细胞的静息膜电位去极化，但不能使NG108 - 15细胞的静息膜电位去极化，并且这种作用被巴弗洛霉素消除。细胞内pH从7.3降低到6.8可抑制药物敏感和耐药细胞的容积敏感性Cl⁻电流。巴弗洛霉素可阻止药物敏感和耐药细胞中Cl⁻电流的激活，而维拉帕米仅抑制NG/DOXR细胞中的Cl⁻电流。本文根据细胞质pH和膜电位在多药耐药中的作用对结果进行了讨论。
