title: Water permeability of mammalian cells as a function of temperature in the presence of dimethylsulfoxide: correlation with the state of the membrane lipids.
abstract: The water permeability of V-79 Chinese hamster lung fibroblasts was determined by measuring the rate of cell shrinkage in hypertonic medium using a cell sizer. The water permeability appears to follow Arrhenius kinetics as a function of temperature with a sharp discontinuity at 21 degrees C. An activation energy of 7.0 +/- 1.6 kcal/mole was found below 21 degrees C and 22.8 +/- 3.1 kcal/mole above 21 degrees C. The correlation time of rotation of the spin label 2,2-dimethyl-5-dodecyl-5-methyloxazolidine-N-oxide was measured as a function of temperature in the cellular membranes, and shows a break at 20 degrees C. A discontinuity was also found in the membrane to water partitioning of the spin label 2,2-dimethyl-5-pentyl-5-butyloxazolidine-N-oxide near 20 degrees C. These breaks may correspond to a membrane lipid phase transition. Dimethylsulfoxide, in the concentration range of 0.2--0.5 M, decreases the water permeability by a factor of two.
mesh_terms: D000818:Animals; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects*; D006224:Cricetinae; D004121:Dimethyl Sulfoxide / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004578:Electron Spin Resonance Spectroscopy; D005990:Glycerol / Q000494:pharmacology; D008168:Lung; D008433:Mathematics; D008563:Membrane Lipids / Q000502:physiology*; D013395:Sucrose / Q000494:pharmacology; D013696:Temperature; D014867:Water / Q000378:metabolism*
chemical_list: D008563:Membrane Lipids; D014867:Water; D013395:Sucrose; D005990:Glycerol; D004121:Dimethyl Sulfoxide