PLASMA-MEMBRANE STUDIES ON DRUG SENSITIVE AND RESISTANT CELL-LINES .3. BIPHASIC KINETICS OF OUABAIN BINDING

Ouabain binding to wild type and ouabain resistant cell lines derived from the murine plasmocvtoma MOPC 173 was studied on cells grown as monolayers. Biphasic kinetics of ouabain binding was observed; the early phase took place within 30 sec, followed by a spontaneous release of the bound ouabain. Then, the late phase was complete after 1-2 hr. This phenomenon was much more pronounced in fibroblastic than in epithclioid cell lines, regardless of their respective drug sensitivity. Ouabain resistant cells when compared to their wild type counterparts did not exhibit drastic changes either in the number or in the affinity of their respective ouabain binding sites. In contrast, the number and affinity of ouabain binding sites were quite different in fibroblastic and in epithelioid cell lines. © 1979.