Effect of ouabain resistance on human diploid fibroblasts carrying other genetic variants

Human skin fibroblasts from a Lesch-Nyhan male with the G6PD A variant and those from a female with the cri-du-chat deletion have been treated with ethyl methane sulfonate and subjected to ouabain selection. Sixteen ouabain-resistant clones were obtained from 1.2 × l0⁸ cells plated in 10^-6 M ouabain. Some variation in degree of ouabain resistance was noted among subclones. The ouabain-resistant phenotype was stable and was associated with G6PD and HGPRT phenotypes and karyotypes similar to the parent strains except that tetraploidy characterized 2 of 5 of the clones karyotyped. The ouabain-resistant cells were used to study the influence of the mutation leading to ouabain resistance on the transfer of nucleotides from cell to cell. Results indicate that contact-feeding of nucleotides is not dependent upon the ouabain-sensitive Na⁺K⁺ transport system. It is suggested that ouabain resistance may provide a simple assay to detect agents mutagenic for human cells, and that cells carrying both HGPRT as well as ouabain-resistant markers are ideal for cell hybridization with strains having no selectable markers.