Increase in adenosine triphosphatase activity of Ehrlich ascites tumor cells following serial cultivation in media with increased (hypertonic) NaCl content.

The cellular activity of ouabain-sensitive sodium-potassium-activated adenosine triphosphatase (Na+-K+-ATPase) and ouabain-insensitive Mg++-ATPase was analysed in sublines of Ehrlich ascites tumor cells serially cultivated either in isotonic media or in media with progressively increased NaCl concentration (up to 0.40 ᴍ). Progressive elevation in the NaCl content of the medium resulted in a progressive increase of cellular ATPase activity, Na+-K+-ATPase thereby being more affected than Mg++-ATPase. These alterations in ATPase activities are interpreted as “adaptive” changes in response to the elevated ionic environment, since “readaptation” of these “high-salt”-tolerant cells to growth in isotonic media resulted in a reversion of the enzyme activities to the level characteristic of the original parent cells.