Development of thermotolerance in mouse fibroblast LM cells with modified membranes and after procaine treatment.

Mouse fibroblast LM cells have been modified with respect to the content of polyunsaturated fatty acyl (PUFA) chains of the membrane phospholipids. The membranes of the modified cells were enriched in PUFA chains and were more fluid as compared to the normal cells, as judged by fluorescence polarization measurements. The thermosensitivity of the PUFA-substituted cells was enhanced. Thermotolerance in the PUFA-substituted fibroblasts could be induced to the same extent as in the nonsubstituted cells. The thermosensitivity in both the PUFA and the nonsubstituted fibroblasts could be enhanced by the treatment of procaine. Procaine could inhibit the triggering as well as the induction of thermotolerance. It is supposed that the mechanism of heat sensitization by procaine is different from the mechanism of preventing thermotolerance induction. The clinical implications of this finding are discussed.