Cationic fluorescent dye Rhodamine 123 (Rh 123) is selectively accumulated in mitochondria on living cells, reflecting the mitochondrial transmembrane potentials. A rapid redistribution of mitochondria to the perinuclear region has been showed by heat treatment. Whereas, these changes of localization after heat treatment were inhibited by addition of Cholcemid. On HeLa cells and colon26 cells, we have studied the growth curve and clonogenic ability to evaluate heat sensitivity and Rh 123 uptake was estimated in concurrence. The decrease in Rh 123 uptake correlated with the loss of clonogenic ability. It was suggested that the uptake of Rh 123 is a useful marker to estimate whether the cell viability after heat treatment exists or not.
