Enhancement of hyperthermic killing cultured mammalian cells by treatment with anisotonic NaCl or medium solutions

Abstract

The exposure of cultured Chinese hamster cells (CHO) to anisotonic medium increased the cellular sensitivity to heat treatment at 42.3°C. A greater potentiation of heat killing is observed when the anisotonic solution consists of pure NaCl in water compared to growth medium made anisoltonic by dilution or by addition of NaCl. Hypertonic treatment caused greater heat sensitization than hypotonic treatment. Thermal tolerance observed in the control cells after 4–6 hours of heating in medium was also observed for cells exposed to anisotonic media during heating if the heating period was greater than 4 h. The exposure of cells to anisotonic media during heating if the heating period was greater than 4 h. The exposure of cells to anisotonic NaCl solutions during heating removed the shoulder from the heat survival curve, while the curves for cells heated in medium made anisotonic retained their shoulders. These studies suggest: (1) that either the plasma membrane is a primary target for heat inactivation of mammalian cells, or (2) that changes in intracellular ion concentrations enhance thermal damage occurring in critical intracellular structures.