Hyperthermia-induced increase in potassium transport in Chinese hamster cells.

Abstract

AbstractThe effect of hyperthermia (42°C) on K+ transport has been examined by monitoring the uptake of 42KCl by Chinese hamster (line CHO) cells at both 37° and 42°C as well as 37°C following a 30‐min treatment at 42°C. Early studies showed that CHO cells exhibit two components of uptake at both 37° and 42°C. Consequently, it was necessary to determine rate equations describing a three‐compartment system (i.e., the bathing medium and two cell‐associated compartments) and apply them to this system. Using the equations describing the behavior of the tracer in each compartment as well as the general solutions given by Robertson et al (1957), a method was developed for obtaining the two components of influx. The two transport rates were determined from equations arising from mathematical analysis and requiring only measurable quantities for their solutions. The results of this study showed that (1) both components of influx at 42°C are increased over influx at 37°C; (2) the increase is significant (by an average 68% for the rapid component and 55% for the slow component); and (3) the increase is due entirely to an increase in active transport. The increased active transport is both immediate and quickly reversible when cells are returned to 37°C; resumption of cell division is delayed for several additional hours, indicating that changes in potassium transport are not directly responsible for the prolonged delay in cell division. Rather, the results suggest that increased activity of the membrane pump may be the initial event in a series of events resulting from heat treatment.