Stimulatory Effect of Insulin on Glucose Metabolism of Thymus Lymphocytes

The effect of insulin and cortisol on glucose metabolism of thymus lymphocytes from adrenalectomized rats was studied. The addition of 10 -8 M insulin increased glucose uptake, lactate production and the production of 14 CO 2 from labeled glucose at an initial concentration of 1.1 mM. Insulin stimulation of glucose metabolism was antagonized by 10 -6 M Cortisol, which inhibited glucose metabolism with or without insulin present. At a glucose substrate concentration of 11 mM, it was not technically possible to measure glucose uptake, but the presence of 10 -8 M insulin increased lactate production 32% and caused a small but statistically significant increase in glycogen content. As with the lower substrate concentration, 10 -8 M cortisol opposed the effects of insulin by decreasing both lactate production and glycogen content of the cells. It may be concluded that thymus lymphocytes can display insulin sensitivity under physiologic conditions.