The role of ubiquinones in regulating lipid metabolism in rat thymocytes

The effects of ubiquinones Q-1, Q-2, Q-8 and Q-9 on lipid biosynthesis in thymocytes in vitro were studied during incubation of cells with ubiquinones within the concentration range of 1-100 mM. A 2-fold inhibition of cholesterol synthesis in thymocytes by ubiquinone Q-9 occurred, when the exogenous ubiquinone concentration in the medium was no less than 40 mM. Incubation of thymocytes with unrelated ubiquinone (Q-1 and Q-2-40 and 100 mM, respectively) resulted in the inhibition of cholesterol synthesis. The inhibiting effect was of the same order of magnitude as that during incubation with ubiquinone Q-9. Ubiquinone Q-8 showed a tendency to inhibit cholesterol synthesis in rat thymocytes. The inhibiting effect of ubiquinone on cholesterol metabolism in thymocytes is specific and is not coupled with fatty acid metabolism.