Dose-dependent influence of hydrocortisone on energy metabolism of rat thymocytes

The dose-dependent influence of hydrocortisone on the energetics of rat thymocytes has been studied. Prolonged action of hydrocortisone in vivo (20 mu g per kg body weight for 6 days daily) and preincubation of thymocytes with hydrocortisone (10 mu M) in vitro resulted in cytotoxicity, the complete uncoupling of oxidative phosphorylation, and a decrease in electron transfer in the mitochondrial respiration chain. A single injection of hydrocortisone (20 mu g/kg 72 h before sacrifice) resulted in the uncoupling of oxidative phosphorylation. Short-term exposure to hydrocortisone (20 mu g/kg 3 h before sacrifice) and also preincubation of thymocytes with hydrocortisone (1 mu M) stimulated electron transport, including substrate oxidation, without uncoupling of oxidative phosphorylation. Short-term exposure to hydrocortisone in vivo inhibited respiration when glucose was used as the oxidation substrate and stimulated respiration in medium containing sodium pyruvate.