Enhancement of thermal killing by polyamines. I. Survival of Chinese hamster cells.

Exposure of Chinese hamster cells to polyamines at an elevated temperature (42 degrees C) results in synergistic cell killing. The effectiveness of polyamines in potentiating thermal killing decreases in the following order: spermine greater than spermidine greater than cadaverine greater than putrescine. The magnitude of the synergism increases with exposure time. The survival curves, when plotted as a function of polyamine concentration, display a shoulder during 1 h exposure at 42 degrees C, followed by exponential cell killing. Longer exposure times eliminate the shoulder and result in steeper slopes of the survival curves. The effect is maximal when exposure to polyamines and heat is simultaneous. Separation in time between the two treatments causes a rapid disappearance of the synergism. The order of application is of only minor importance in this regard. The results suggest that the intracellular level of spermine may be a major factor in determining heat sensitivity of Chinese hamster cells.