Thermal instability of red blood cell membrane bilayers: Temperature dependence of hemolysis

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Abstract
Rates of human red blood cell hemolysis were measured as a function of temperature. Three distinct temperature intervals for hemolysis were noted: a) At temperatures equal to or less than 37°C no hemolysis was observed for the duration of the incubation (30 hr). b) For temperatures exceeding 45°C hemolysis rates are rapid and are accompanied by gross changes in cellular morphology. The activation energy for hemolysis is 80 kcal/mole; this value is characteristic of protein denaturation and enzyme inactivation suggesting that these processes contribute to hemolysis at these high temperatures. c) Between 38 and 45°C the energy of activation is 29 kcal/mole, indicating that a fundamentally different process than protein inactivation is responsible for hemolysis at these relatively low temperatures. A mechanism based on the concept of the critical bilayer assembly temperature of cell membranes (N.L. Gershfeld,Biophys. J. 50:457–461, 1986) accounts for hemolysis at these relatively mild temperatures: The unilamellar state of the membrane is stable at 37°C, but is transformed to a multibilayer when the temperature is raised; hemolysis results because formation of the multibilayer requires exposing lipid-free areas of the erythrocyte surface. An analysis of the activation energy for hemolysis is presented that is consistent with the proposed unilamellar-multibilayer transformation.