Effects of cold stress on mitochondrial oxidative phosphorylation

Abstract

The P:O ratio with succinate as substrate is the same for liver mitochondria from ‘cold-fasted’ rats as it is for mitochondria from control rats. Glucose-hexokinase acceptor studies with either succinate or glutamate as substrate indicate that the oxidative phosphorylating system is about as tightly coupled in the liver mitochondria from cold-fasted rats as it is in those from control rats. These results were surprising since earlier work with liver homogenates indicated that the efficiency of oxidative phosphorylation is markedly reduced in the homogenate from cold-fasted rats. The possible reasons for these differences in results with homogenates on the one hand and mitochondria on the other are discussed. The use of mitochondrial activities as an index of the efficiency of oxidative phosphorylation in vivo is also discussed.