Effects of Nystatin on Intracellular Contents and Membrane Transport of Alkali Cations, and Cell Volume in HeLa Cells

Nystatin (50 micrograms/ml) had strong influence on the intracellular contents and membrane transports of monovalent ions and water in HeLa cells. The nystatin-induced changes in the intracellular ion content and cell volume were inhibited by sucrose, and Donnan and osmotic equilibria were attained. Using cells under conditions for these equilibria, the concentrations of intracellular impermeant solutes, their mean valence, the differences of their intra- and extracellular osmotic concentrations, and the circumferential tension of the cell membrane were determined. Stimulation by nystatin of the influx of one cation species, e.g. Rb, was inhibited by another cation species, e.g. Na. The stimulatory effect of nystatin on cation fluxes was reversible within 1 hr after ionophore addition, and after 1-hr treatment the intracellular contents of Na and K became proportional to their extracellular concentrations, provided that the sum of these concentrations was constant (300 mM). Similar proportionality was also observed in the presence of choline, provided that the choline concentration was less than those of the alkali cations. The implications of these results in relation to the osmotic properties of cultured cells, and the experimental regulation of alkali cations in the cells, are discussed.