DOSE-DEPENDENT INFLUENCE OF HYDROCORTISONE ON ENERGY-METABOLISM OF RAT THYMOCYTES

The dose-dependent influence of hydrocortisone on the energetics of ra t thymocytes has been studied. Prolonged action of hydrocortisone in v ivo (20 mu g per kg body weight for 6 days daily) and preincubation of thymocytes with hydrocortisone (10 mu M) in vitro resulted in cytotox icity, the complete uncoupling of oxidative phosphorylation, and a dec rease in electron transfer in the mitochondrial respiration chain. A s ingle injection of hydrocortisone (20 mu g/kg 72 h before sacrifice) r esulted in the uncoupling of oxidative phosphorylation. Short-term exp osure to hydrocortisone (20 mu g/kg 3 h before sacrifice) and also pre incubation of thymocytes with hydrocortisone (1 mu M) stimulated elect ron transport, including substrate oxidation, without uncoupling of ox idative phosphorylation. Short-term exposure to hydrocortisone in vivo inhibited respiration when glucose was used as the oxidation substrat e and stimulated respiration in medium containing sodium pyruvate.