title: Effects of hyperthermia and membrane-active compounds or low pH on the membrane fluidity of Chinese hamster ovary cells.
abstract: Chinese hamster ovary (CHO) cells heated in the presence of the membrane-active agents procaine, ethanol, butylated hydroxytoluene (BHT) and glycerol were analysed for changes in fluorescence polarization of the lipid probe (1-[4(trimethylamino)phenyl]-6-phenyl-1,3,5-hexatriene, an indicator of plasma membrane fluidity). Cells were heated in normal and acid (pH 6.6) medium. Procaine, ethanol, BHT and low pH sensitized cells to heat-killing. Procaine, ethanol and BHT decreased fluorescence polarization (increased plasma membrane fluidity) significantly. Polarization distributions for cells heated with these sensitizers were broadened substantially and were skewed toward lower polarization values. Glycerol, a heat-protector, inhibited changes in fluorescence polarization due to heating at temperatures up to 45.0 degrees C. Heating cells at either 42 or 45 degrees C in pH 6.6 medium had no significant effect on the fluorescence polarization compared with controls, while survival was reduced substantially. Thus, heat-sensitization of low pH cannot be ascribed to changes in membrane fluidity. The changes in membrane fluidity caused by other sensitizers and protector indicate that membrane fluidity changes may be a contributing cause of cell killing by hyperthermia.
authors.affiliation: Department of Radiological Health Sciences, Colorado State University, Fort Collins 80523.
authors.forename: J R
authors.initials: JR
authors.lastname: Dynlacht
authors.forename: M H
authors.initials: MH
authors.lastname: Fox
mesh_terms: D000818:Animals; D002084:Butylated Hydroxytoluene / Q000494:pharmacology; D016466:CHO Cells / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D000431:Ethanol / Q000494:pharmacology; D005434:Flow Cytometry; D005454:Fluorescence Polarization; D005990:Glycerol / Q000494:pharmacology; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008560:Membrane Fluidity / Q000187:drug effects; D011343:Procaine / Q000494:pharmacology
chemical_list: D002084:Butylated Hydroxytoluene; D000431:Ethanol; D011343:Procaine; D005990:Glycerol