In vitro insulin-stimulated conversion of [U-14C]glucose to 14CO2 by rat thymocytes

Addition of bovine insulin to thymocytes from adrenalectomized rats resulted in stimulation of [U-14C]glucose conversion to 14CO2. A significant enhancement of 14CO2 formation by insulin occurred by 30 min of incubation, and was consistently observed at an insulin concentration of 10(-8) M. The response to insulin was similar at 0.55 and 1.1 mM glucose, and was obtained at three cell concentrations (0.5, 1.0, 2.0 X 10(8) cells/ml). The incorporation of [3H]leucine into trichloroacetic acid-precipitable material was significantly increased by 10(-6) and 10(-8) M insulin. Cycloheximide, at a level of 2.5 X 10(-5) M, suppressed [3H]leucine incorporation by 93% and inhibited the stimulation of 14CO2 formation by insulin. We conclude that insulin can enhance the formation of 14CO2 from [U-14C]glucose by thymocytes in vitro, and that this response may require the synthesis of one or more proteins.