PLASMA-MEMBRANE STUDIES ON DRUG-SENSITIVE AND DRUG-RESISTANT CELL LINES .2. OUABAIN SENSITIVITY OF (NA++K+)-STIMULATED MG2+-ATPASE

Mutant cell lines were selected from the mouse plasmocytoma MOPC 173 for their resistance to ouabain, dibutyryl cyclic AMP, theophylline and concanavalin A. Three wild type cell lines were compared with their 7 resistant counterparts. All resistant mutants exhibited a (Na+ + K+)-stimulated Mg2+-ATPase resistance to ouabain inhibition when measured in microsomes. The homogeneity of ouabain binding sites was found in most of the cell lines. Two populations of sites were detected in 1 wild type 1 resistant cell line. The (Na+ + K+)-ATPase-ouabain interaction is modulated by a nonspecific membrane structure.