Chinese hamster ovary (CHO) cells were exposed to various concentrations of diethylmaleate (DEM) during a 42°C incubation to determine if glutathione (GSH) compartmentalization was a factor in modification of thermal sensitivity. Cytoplasmic and mitochondrial GSH were isolated from CHO cells immediately after a hyperthermic treatment consisting of 2 h at 42°C. Under these experimental conditions differential GSH depletion between the cytosol and mitochondrial compartments were observed. For example, 12 μM DEM was needed to deplete cytoplasmic GSH by 50% compared to 24 μM DEM needed to deplete mitochondrial GSH to the same level. Further, an In-In plot of the relative cytosolic GSH concentration vs the DEM concentration indicated a linear relationship (slope = -1.0). In contrast, the mitochondrial GSH plot exhibited a shoulder followed by a linear removal (slope = -0.90). Essentially the two linear curves were parallel. Analysis of thermal dose-response curves for cells exposed to between 10 and 100 μM DEM indicated that cell survival was unaffected by the addition of DEM until a critical concentration was surpassed. This threshold response was interpreted to mean that mitochondrial GSH depletion was the limiting factor.

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