Relationship between Hyperthermic Cell Killing and Protein Denaturation by Alcohols

Abstract

The monohydric alcohols methanol, ethanol, 2-propanol, and tert.-butanol dramatically sensitize V79 Chinese hamster lung cells to hyperthermia. for concentrations less than 3% alcohol by weignt, the rate of cell inactivation (k) appears to vary exponentially as a function of alcohol concentration. The degree of sensitization increases with increasing chain length, and for a constant concentration the ratio of the k's is 1:1.3:1.8:3.1 for methanol, ethanol, 2-propanol, and t-butanol, respectively. Mono-, di-, and trihydric alcohols have similar effects upon the rate of protein denaturation. Membrane lipid fluidity of V79 cells was determined from 23 to 63/sup 0/C by measuring the rotational correlation time of the spin label 2,2-dimethyl-5-dodecyl-5-methyloxazolidine-N-oxide (2N14). A straight line was found for the Arrhenius plot of tau/sub c/, with an activation energy of 4.82 +- 0.07 kcal/mole. From the Arrhenius plot of the rate of cell killing from 42.0 to 46.8/sup 0/C, the enthalpy (..delta..H) and entropy (..delta..S) of activation were found to be 146 +- 9 kcal/mole and 388 cal/mole K, respectively. These values are consistent with protein denaturation (or possibly the denaturation of some other macromolecule) being the rate-limiting step in hyperthermic cell killing.