Enhancement of thermal killing by polyamines. II. Uptake and metabolism of exogenous polyamines in hyperthermic chinese hamster cells

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Abstract
The uptake and metabolism of the polyamines spermine, spermidine, cadaverine and putrescine, previously shown to potentiate heat sensitivity, were studied in cultured Chinese hamster cells. Heat (42°C) causes enhanced uptake of exogenously supplied polyamines into the acid‐soluble fraction of the cells. Putrescine is taken up exceptionally fast at 37°C, about 10 times faster than its homologue, cadaverine. This uptake is slower at 42°C. The polyamines taken up were metabolized to some extent and the metabolites were similar at 37°C and 42°C except in the case of putrescine. These results suggest that potentiation of heat‐sensitivity is probably mediated by the polyamines as such and not by their metabolites. Polyamines slightly protect the cells against the inhibitory effect of heat on RNA and protein synthesis. It is suggested that exogenous polyamines interact with nucleic acids inside the cell, and this interaction may underlie their synergism with heat. The exact nature of this interaction and the way it leads to enhanced thermal sensitivity are still obscure.