Using rat liver mitochondria we determined that the primary biochemical target for inhibition of mitochondrial bioenergetic function by rhodamine 123 (Rh123) was FoF1-ATPase and that the amount of Rh123 associated with mitochondria is proportional to the mitochondrial membrane potential. Inhibition of coupled respiration by Rh123 in mitochondria isolated from CX-1, a Rh123-sensitive carcinoma cell type, and CV-1, a Rh123-insensitive normal epithelial cell type, was linearly related to the amount of Rh123 added (micrograms/mg protein) with CX-1 mitochondria exhibiting 2-fold greater inhibition compared to CV-1 mitochondria at any given amount of dye. The inhibition pattern for mitochondria isolated from MIP101, a Rh123-insensitive carcinoma cell type, was nonlinear, exhibiting greater sensitivity than CV-1 mitochondria at very low amounts of Rh123 but becoming less sensitive than either CV-1 or CX-1 at higher amounts. Rh123 inhibited FoF1-ATPase activity to a similar extent and in a concentration-dependent manner in both CV-1 and CX-1 mitochondria, but a different and complex pattern of inhibition was apparent for MIP101 mitochondria. Moreover, mitochondria from the 2 carcinoma cell types, CX-1 and MIP101, had higher membrane potentials (163 +/- 7 and 158 +/- 8 mV, respectively) than did mitochondria from the normal epithelial cell type, CV-1 (104 +/- 9 mV). It was concluded that differences in both mitochondrial membrane potential and sensitivity of FoF1-ATPase contribute to the selective cytotoxicity exhibited by Rh123 for certain cell types in vitro.

中文翻译：

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罗丹明123选择性细胞毒性的基础。

使用大鼠肝线粒体，我们确定若丹明123（Rh123）抑制线粒体生物能功能的主要生化目标是FoF1-ATPase，并且与线粒体相关的Rh123的量与线粒体膜电位成正比。Rh123抑制线粒体对呼吸的耦合作用，线粒体从CX-1（对Rh123敏感的癌细胞类型）和CV-1（对Rh123不敏感的正常上皮细胞类型）中分离出来，与Rh123的添加量呈线性关系（微克/毫克蛋白），在任何给定的染料量下，与CV-1线粒体相比，CX-1线粒体均表现出2倍的抑制作用。从对Rh123不敏感的癌细胞类型MIP101分离的线粒体的抑制模式是非线性的，在非常低的Rh123量下显示比CV-1线粒体更高的灵敏度，但在更高量的条件下比CV-1或CX-1灵敏度低。Rh123在CV-1和CX-1线粒体中以相似的程度和浓度依赖性的方式抑制FoF1-ATPase活性，但是对于MIP101线粒体，抑制作用却明显不同。此外，来自两种癌细胞类型CX-1和MIP101的线粒体具有比来自正常上皮细胞类型CV-1的线粒体更高的膜电位（分别为163 +/- 7和158 +/- 8 mV）（ 104 +/- 9 mV）。结论是线粒体膜电位和FoF1-ATPase敏感性的差异有助于Rh123在体外对某些细胞类型表现出的选择性细胞毒性。