Effect of external K+ on protein and DNA synthesis during and after heat shock in rat hepatoma cells.

Abstract

The effects of extracellular K+ concentrations on protein and DNA synthesis after non-lethal heat shock were studied in the hepatoma cell lines Reuber H35 and HTC. Elevation of the extracellular K+ concentration by equimolar replacement of Na+ by K+ in growth media of Reuber H35 and HTC cells caused an increase of the intracellular K+ content in both cell lines. This property was subsequently used to study the effect of elevated intracellular K+ concentrations on protein and DNA synthesis after hyperthermic treatment at 42 degrees C for 30 min. In normal K+ medium, protein and DNA synthesis were inhibited rapidly after the start of the hyperthermic treatment in both Reuber H35 and HTC cells. Increasing the external K+ concentration of the medium did not influence the inhibition and subsequent recovery of protein synthesis after heat shock in both cell lines. In contrast, in media with elevated K+ concentrations, DNA synthesis after heat-shock was inhibited less in Reuber H35 cells than in cells incubated in normal K+ medium and, furthermore, showed no inhibition in HTC cells. The protective effect of external K+ on DNA synthesis after heat shock was maximal between 50 and 70 mM in the temperature range 42-44 degrees C.