A comparative study of the transport of pyruvate in liver mitochondria from normal and diabetic rats

A comparative study of the transport of pyruvate in liver mitochondria from normal and diabetic rats has been carried out. The Km for the pyruvate uptake in diabetic, ketotic mitochondria is practically equal to that measured in normal mitochondria, while the Vmax is significantly lower. The lower activity of the pyruvate translocator in diabetic mitochondria compared to normal mitochondria is also shown by swelling experiments as well as by following the rate of pyruvate-supported respiration. Pre-exposure of mitochondria from normal rats to the ketone body acetoacetate and to 2-oxobutyrate results in a decrease of the Km for pyruvate uptake. This effect is impaired in mitochondria from diabetic animals. The results indicate that the activity and the properties of the mitochondrial pyruvate translocator are modified in the diabetic, ketotic condition.