Anaerobic glycolysis of slices and homogenates of liver from thyroxine injected rats

The rates of anaerobic lactate and total acid production from glucose by liver slices of normal and thyroxine-injected rats have been determined and compared. The results indicate that observed differences in slice glycolytic response were due to changes in liver glycogen content and not to the thyroid state of the animal. On the other hand, the potential anaerobic glycolytic rate of hyperthyroid livers as measured by the homogenate technique has been shown to be 30% greater than normal when fructose-1,6-diphosphate (HDP) is the substrate, and 60% greater than normal when both HDP and glucose are present as substrates. With glucose alone as substrate, the glycolytic activity of both types of homogenates is less than one-tenth that found when HDP is the sole substrate. The presence of a rate-limiting enzymatic step in the breakdown of glucose, located between the latter and HDP, must therefore be considered when either a normal or hyperthyroid liver homogenate is employed.