Search

Low ouabain concentration (1 x 10(-6) M) is shown to decrease intracellular K+ (K+in) and to increase intracellular Na+ (Na+in) in human fibroblast cell cultures. The same ouabain concentration was without effect upon K+in ad Na+in in rodent cultures such as BHK-21, mouse fibroblasts and rat glyoma C6 cells. K+in and Na+in in the mixed cultures of human and BHK-21 fibroblasts or human and mouse fibroblasts were found to be resistant to 1 x 10(-6) M ouabain whereas that of the mixtures of human and rat glyoma C6 cells proved to be ouabain-sensitive. The gap-junction-mediated dye transfer was revealed between human and BHK-21 cells. Such an effect was very small in the human-C6 cell mixed culture. It is concluded that cells with active ion pumps can support the maintenance of K+ and Na+ gradients in cells with inactive pumps, provided that effective ion transport via gap junctions takes place.

Animal cell cooperation has been studied in a mixed cell culture. Membrane potentials of human embryonic cells and hamster BHK-21 cells were recorded by intracellular microelectrodes. The Na+/K(+)-ATPase inhibitor ouabain (1 x 10(-6) M; 2 h) caused strong depolarisation of the human cells in pure culture. The same treatment reduced only slightly the membrane potential in the hamster cells in pure or mixed cultures, as well as in the human cells in mixed culture. The above data can be explained by effective ion fluxes through heterotypic gap junctions in mixed culture. Thus, in the presence of ouabain the Na+/K(+)-ATPase of hamster cells creates transmembrane differences of the electrochemical potential of ions not only in the hamster cells, but in the human cells as well.