Effect of membrane fatty acid substitution and temperature on repair of sublethal damage in mammalian cells.

Repair of sublethal radiation damage (SLD) has been investigated as a function of temperature in mouse fibroblast LM cells with different membrane lipid composition. Rigidification or fluidization of the cellular membranes was accomplished by incorporation of myristic acid and arachidonic acid, respectively, in the phospholipids of the membranes. The SLD repair after radiation was essentially the same for the cells with the more rigid (saturated fatty acid) membranes and the cells with the more fluid (polyunsaturated fatty acid) membranes. This observation was made for repair at 37 degrees C as well as for repair at hypothermic temperatures. Incorporation of polyunsaturated fatty acid protected the cells against hypothermic death. These experiments demonstrate that although membranes are likely targets for cell killing by low temperature treatments, membrane lipids are probably not involved in the repair of sublethal radiation damage. It must be concluded that neither the degree of polyunsaturation of the lipids nor the degree of fluidity of the membrane is important for radiation-induced killing of mammalian cells.