Correlation Between Amounts of Cellular Membrane Components and Sensitivity to Hyperthermia in a Variety of Mammalian Cell Lines in Culture

The weight ratio of either cholesterol or phospholipid to protein contents in 7 different cell lines, growing exponentially at 37°, correlates positively with increasing resistance of the cells to subsequent hyperthermic cell killing. The relative heat resistance of each cell line is derived from survival curves obtained when the different cell lines are exposed to 43°. Cholesterol and phospholipid amounts in the particulate fraction correlate with survival sensitivity to 43° when the values are expressed per mg protein but not when expressed per cell number. Also, cholesterol:phospholipid molar ratios and the amount of protein in the particulate fraction do not display linear correlations with sensitivity of the respective cell lines to 43°-induced cell killing. The relative degree of fatty acid saturation at 37° also is independent of whether cells show a higher degree of heat resistance. These data suggest that lipid (both cholesterol and phospholipid):protein weight ratios correlate with increasing resistance of cells to an elevation in temperature. The major implication of these data is that major membrane components can influence and perhaps predict cellular survival to hyperthermia.