Reversible organization of mitochondria into associations as a factor regulating respiration

Mitochondria in the form of associations close to their state in the quiescent cell were obtained in rat liver homogenate under physiological for cytosol concentrations of potassium and calcium ions and small dilution of tissue. Associations in such homogenates are stable on storage in ice for several hours. Dissociation of associations is induced by dilution of the homogenate, addition of EDTA, or by administration of adrenaline to the animal. Respiration rate is increased and ADP/O ratio is decreased when associations dissociate. The observed increase in respiratory rate induced by adrenaline administration in vivo is decreased or abolished when associations are dissociated in the incubation medium induced by influences in vitro. This is due to hyperactivation of respiration which leads to inhibition of succinate oxidation by oxaloacetate. Under the conditions preserving the associations of mitochondria a close interaction of oxidative and transamination processes is observed as well as a broader range of metabolic states of mitochondria than in standard preparations which dissipate into single granules on isolation in sucrose, high dilution, and washing.