Ledbetter M L, Lubin M
J Cell Biol. 1979 Jan;80(1):150-65. doi: 10.1083/jcb.80.1.150.
Mammalian cells of different species differ in sensitivity to ouabain. This sensitivity is expressed as reduced intracellular K+ content, reduced rates of protein synthesis, and cessation of cell multiplication. Using 86Rb+ as a measure of intracellular K+, we found higher levels of radioactivity in mixtures of ouabain-sensitive and -resistant cells cultured in the presence of ouabain than predicted from pure cultures of the two component cell types. The simplest explanation is that K+ and 86Rb+ are being transferred from ouabain-resistant to ouabain-sensitive cells, enhancing the total intracellular 86Rb+ in the culture. A function, "index of cooperation," expresses this enhancement as a number ranging from 0 to 1, and permits comparisons to be made under various culture conditions and using various cell types. An index of cooperation greater than 0 requires cell contact, since no enhancement occurs when contact between two cell types in the same culture is prevented. The index of cooperation for a number of different cell combinations agrees with other measures of cell-cell interaction associated with gap junctions, such as electrical coupling and metabolic cooperation. Coculture of ouabain-sensitive and ouabain-resistant cells in the presence of ouabain also leads to restoration of the capacity for protein synthesis. Autoradiography shows that this restoration occurs in the sensitive cell type and is dependent upon contact with ouabain-resistant cells. Furthermore, sensitive cells are able to multiply in the presence of ouabain when cocultured with resistant cells. Thus K+, presumably transferred to sensitive cells through gap junctions, is able to counteract the toxic effects of ouabain on intracellular K+ levels and protein synthesis, and to restore growth.
不同物种的哺乳动物细胞对哇巴因的敏感性存在差异。这种敏感性表现为细胞内钾离子含量降低、蛋白质合成速率下降以及细胞增殖停止。使用⁸⁶Rb⁺作为细胞内钾离子的衡量指标，我们发现在哇巴因存在的情况下培养的哇巴因敏感细胞和抗性细胞混合物中的放射性水平高于根据两种组成细胞类型的纯培养所预测的水平。最简单的解释是钾离子和⁸⁶Rb⁺正在从哇巴因抗性细胞转移到哇巴因敏感细胞，从而提高了培养物中细胞内总的⁸⁶Rb⁺含量。一个“合作指数”函数将这种增强表示为一个从0到1的数字，并允许在各种培养条件下和使用各种细胞类型进行比较。大于0的合作指数需要细胞接触，因为当同一培养物中两种细胞类型之间的接触被阻止时不会发生增强。许多不同细胞组合的合作指数与其他与间隙连接相关的细胞间相互作用的测量结果一致，如电偶联和代谢合作。在哇巴因存在的情况下将哇巴因敏感细胞和抗性细胞共培养也会导致蛋白质合成能力的恢复。放射自显影显示这种恢复发生在敏感细胞类型中，并且依赖于与哇巴因抗性细胞的接触。此外，当与抗性细胞共培养时，敏感细胞能够在哇巴因存在的情况下增殖。因此，可能通过间隙连接转移到敏感细胞的钾离子能够抵消哇巴因对细胞内钾离子水平和蛋白质合成的毒性作用，并恢复生长。
