The effect of hyperthermia on glucose transport in normal and thermal-tolerant Chinese hamster ovary cells

The effect of hyperthermia in combination with melphalan on drug-sensitive and drug-resistant CHO cells in vitro

The effect of temperature on the cytotoxicity of melphalan in a pleiotropic drug-resistant mutant CHO cell line (CHR C5) and in its drug-sensitive parent (Aux B1) was studied in vitro using a clonogenic assay. The cytotoxicity of melphalan was significantly enhanced at elevated but non-lethal temperatures (39-41 degrees C) and hyperthermia potentiated the effect of melphalan in the lethal temperature range (43-44 degrees C) in both cell lines. The effect of temperature on membrane permeability to melphalan was studied to determine whether the increase in cytotoxicity was associated with increased intracellular drug levels. The uptake of 14C-labelled melphalan during 5 min increased with increasing temperature. Drug efflux, however, also increased at elevated temperatures. Intracellular drug levels at equilibrium were increased at elevated temperatures but the magnitude of this effect was small in comparison with the much larger increases in cytotoxicity.

Effect of hyperthermia on the internal microviscosity of erythrocytes and lymphocytes: a spin-label study

The internal microviscosity of human erythrocytes and porcine lymphocytes was investigated, from the electron-spin resonance spectral characteristics of the nitroxyl spin probe, 4-amino-2,2,6,6-tetramethylpiperidinyloxy. Heat-induced permanent damage to cells was observed as an increase in the intracellular microviscosity of nucleate and enucleate cells. Induction of heat resistance was found for erythrocytes treated with a double heat shock.

Does thermotolerance occur in human red cells?

Osmotic fragility and autohemolysis were used as endpoints in the measurement of damage to the plasma membrane in human erythrocytes, after single or double heat treatments. Injury recorded above 46 degrees C, and the induction of thermotolerance in the enucleate cells after a primary heat treatment of 44 degrees C for 15 min, indicates that the plasma membrane plays an important role in heat injury and in thermotolerance.

The effect of hyperthermia on the cytotoxicity of melphalan in Chinese hamster ovary cells

The heat stability of melphalan during incubation at temperatures from 37 degrees C to 45 degrees C was determined by spectrophotometric and HPLC analyses and by direct measurement of melphalan cytotoxicity using a colonogenic assay Although OD 250 changed little during exposure to temperatures up to 45 degrees C for periods of up to 1 h, the melphalan HPLC peak decreased as function of incubation time and temperature. Loss of cytotoxicity following heating paralleled the decay of the melphalan HPLC peak. Despite the inactivation of melphalan by heat, the cytotoxic effects of melphalan were enhanced at elevated temperatures from 38 degrees C to 42 degrees C and synergism was observed at lethal temperatures above 42 degrees C.