Ouabain-resistant mutants of Chinese hamster ovary cells are not directly affected in Na+, K+-ATPase

The nature of biochemical lesions in a number of independent single-step ouabainresistant (OuaR) mutants of Chinese hamster ovary cells has been examined. The cellular uptake of86Rb in the mutant cells was found to be resistant to inhibition by ouabain and correlated with the degree of resistance of the mutants to the drug. However, the plasma membrane Na+, K+-ATPase from all five of the OuaR mutants examined showed similar sensitivity to inhibition by ouabain as seen for the enzyme from the parental sensitive cells. These results provide evidence that, contrary to the general assumption, OuaR mutants of Chinese hamster ovary cells, which are widely used for genetic and quantitative mutagenesis studies, are not directly affected in the Na+, K+-ATPase.