Increase in the contribution of transamination to the respiration of mitochondria during arousal

The involvement of transamination in the respiration of liver mitochondria in ground squirrels during hibernation and arousal has been studied. It was shown by HPLC that, in the presence of glutamate and malate, the formation of alpha-ketoglutarate (KGL), a transamination marker, and fumarate, a product of succinate oxidation, takes place. During arousal, the formation of KGL increased fourfold, and the respiration sensitive to the inhibitor of aspartate transaminase aminooxyacetate (AOA) increased threefold. The function of transamination upon arousal is related to the elimination of oxaloacetate, an endogenous inhibitor of succinate dehydrogenase. In addition, being more resistant to oxidative stress than oxidation, transamination is probably involved in the antioxidant defense required during the rapid rise of body temperature upon arousal. Our experiments showed an increase in the concentration of malonic dialdehyde (MDA), an end product of lipid peroxidation, in liver mitochondria in this state, which can reduce the activity of the enzymes of the tricarboxylic acids cycle. Under these conditions, the transamination contributes to the maintenance of a high respiration rate necessary for arousal.