title: Characterization of a Chinese hamster ovary cell line resistant to uncouplers.
abstract: The chemiosmotic theory of oxidative phosphorylation and the action of uncouplers was examined by characterizing a clone, UH5, of Chinese hamster ovary (CHO TK-) cells resistant to 5-chloro-3-tert-butyl-2'-chloro-4'-nitrosalicylanilide (S-13), a potent uncoupler of oxidative phosphorylation. About 9-times and 4-times more S-13 was required to effect growth and respiration respectively of UH5 cells compared to the parental CHO TK- cells. UH5 cells were cross-resistant to the uncouplers SF-6847 (3,5-di-tert-butyl-4-hydroxy-benzylidenemalononitrile), carbonylcyanide p-trifluoromethoxyphenylhydrazone and 2,4-dinitrophenol but not to oligomycin, venturicidin or Tevenel. Size, chromosome number and DNA content indicated that the UH5 cell line was probably pseudotetraploid compared to the parental pseudodiploid CHO TK- cells. Hybrid and cybrid cells formed from crosses of UH5 cells and cytoplasts, respectively, with an uncoupler-sensitive cell line were sensitive to S-13 indicating that resistance is probably nuclear-determined. UH5 cell mitochondria had increased cytochrome oxidase and decreased H+-ATPase activities. A fivefold resistance of oxidative phosphorylation to uncouplers was found at the mitochondrial level with respiration driven by either succinate or ascorbate/N,N,N',N'-tetramethyl-p-phenylenediamine. In contrast, no difference in sensitivity was found to valinomycin between mitochondria from UH5 and CHO TK- cells. The oligomycin-sensitive H+-ATPase activity of UH5 and CHO TK- cell mitochondria was equally stimulated by the uncoupler S-13. Uncoupler-resistant mitochondria would not be expected on the basis of the chemiosmotic theory, and the relation of the results to other modes of coupling is considered.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001410:Bacillus megaterium / Q000187:drug effects; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004351:Drug Resistance; D005260:Female; D010053:Ovary / Q000187:drug effects*; D010085:Oxidative Phosphorylation; D006180:Proton-Translocating ATPases; D014475:Uncoupling Agents / Q000494:pharmacology*; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D014475:Uncoupling Agents; D014634:Valinomycin; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases