Effects of 2 : 4-Dinitrophenol and Other Agents on the Swelling of Isolated Mitochondria

Abstract

WE have offered evidence¹ that, under various conditions, the swelling of isolated rat-liver mitochondria is dependent on the presence of oxidizable subtrates. For example, if the particles are stored for one day in 0.44 M sucrose at 0° C. (‘aged’), phosphate or thyroxine no longer causes them to swell unless certain oxidizable subtrates, for example, β-hydroxybutyrate, are added as well. Reasons were given for supposing that, in many circumstances, swelling is dependent on mitochondrial respiration. We suggested that, in view of the stabilizing action of 0.1 mM 2 : 4-dinitrophenol², any effect of respiration on swelling may be exerted through coupled phosphorylation (see also ref. 3); however, after a more extensive study of the effects of uncoupling agents we think that this is unlikely to be so. Thus, lower concentrations of 2 : 4-dinitrophenol, and dicoumarol, will, under some conditions, accelerate the swelling induced by phosphate, and even 0.1 mM dinitrophenol will increase the rate of swelling if it is added after the mitochondria have been previously incubated in the presence of phosphate.