1. The effects of non-lethal bacteraemia or endotoxaemia on insulin-stimulated glucose metabolism were studied in isolated, incubated soleus muscle of rats after 24 and 48 h.
2. The insulin-stimulated rates of lactate formation and glycogen synthesis were similar in muscles isolated from control and bacteraemic rats.
3. Endotoxaemia increased the rates of lactate formation, at all levels of insulin, both at 24 h (∼ 32%) and 48 h (∼ 26%). Endotoxaemia did not alter the sensitivity of glycolysis to insulin.
4. Endotoxaemia decreased the rates of glycogen synthesis at all concentrations of insulin both at 24 h (∼ 39%) and 48 h (∼ 23%).
5. The increase in the rate of glycolysis was related in a dose-dependent manner to the amount of endotoxin given to the animals.
6. Endotoxaemia decreased plasma tri-iodothyronine levels (41%). However, the effects of endotoxaemia (48 h) on glucose metabolism in muscle are similar to those caused by hyperthyroidism. In hypothyroid rats, endotoxin administration increased the rates of glycolysis in muscle in vitro.
7. It is concluded that there are enhanced basal and insulin-stimulated rates of glycolysis in soleus muscle from endotoxaemic rats. This may be due to both increased glucose transport and decreased glycogen synthesis.