Microsomal desaturation of stearic acid in relation to lymphocyte activation

The conversion of stearic acid to oleic acid (delta 9-desaturase) was followed in mouse thymocytes stimulated by either concanavalin A or concanavalin A + interleukin-2 resulting in different rates of cell proliferation. To estimate the plasma membrane turnover of oleic acid as compared to that of a saturated fatty acid, double-label experiments ([14C]oleic acid, [3H]palmitic acid) were performed. Following an inhibition delta 9-desaturase was found to be activated from the fourth hour of stimulation. In the early period of cell activation this process proved to be independent of protein synthesis, whereas in the stage of proliferation it was dependent on it. Increased membrane fluidity in the first 30 min of activation is not likely due to enrichment of oleic acid. Cell proliferation and microsomal desaturation seem to be coupled and an increasing amount of oleic acid is at least one of the factors resulting in increased fluidity of the surface membrane of proliferating cells.