Mutagenesis vol. 2 no. 5 pp. 383-389, 1987
© 1987 UK Environmental Mutagen Society/Oxford University Press
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Molecular analysis of ouabain-resistant mutants of the mouse lymphoma cell line L5178Y
MRC Cell Mutation Unit, University of Sussex Falmer, Brighton, E.Sussex BNI 9RR, UK
We have carried out molecular and biochemical analyses on several spontaneous and mutagen-induced ouabain-resistant mutants from the mouse lymphoma cell line L5178Y. Mutant cells were much more resistant than wild-type cells to the toxic effects of ouabain. The gross structures and copy numbers of two ouabain-resistant genes were unaltered in the mutants, as was the expression of the Na, K-ATPase gene. Uptake of 86Rb+ was more resistant to ouabain in the mutants than in wild-type cells. There was no evidence for an inducible uptake mechanism. The Na, K-ATPase activity in extracts of the mutants was, in all cases examined, more resistant than wild-type cells to the inhibitory action of 103 M ouabain. At 105M ouabain, the Na, K-ATPase activity in three out of eleven mutants was actually more sensitive to ouabin than in wild-type cells. These data suggest that the ouabain resistance of the mutants probably results from single basechanges in the alpha subunit of the Na, K-ATPase gene, rather than from amplification or overexpression of ouabain resistance genes. The latter types of alterations have been described for ouabain-resistant lines derived in other laboratories.