Alterations of cellular lipids in rat thymocytes during cell cycle progression

This study provides information on the lipid content and composition of rat thymocytes during cell cycle progression. Cultured rat thymocytes were stimulated by concanavalin A and interleukin-2 to enter the cell cycle and to proliferate. At indicated intervals during a 96 h culture, cells were analyzed for lipid content and lipid synthesis. A growth-related 3.8-fold increase in the cellular cholesterol and a 2.8-fold increase in the phospholipid content was observed after 48 h of culture. Cholesterol synthesis, measured by [14C]acetate incorporation, increased 34-fold, whereas the synthesis of the other lipids was enhanced only 15-fold. Concerning the percentage distribution of the total fatty acids, arachidonic acid showed a significant decline between 24 and 72 h of culture, being mainly caused by the release of arachidonic acid from phosphatidylcholine. Addition of actinomycin D, an inhibitor of DNA replication, prevented the decline of cellular arachidonic acid content in a dose-dependent manner. These data suggest that both the pronounced rise of the cholesterol content as well as the decline of arachidonic acid content are closely linked to cell proliferation.