Effect of sodium oleate on the metabolism and size of rat liver mitochondria I. Uncoupling, shrinkage and their re­versal action by bovine serum albumin

Effects of sodium oleate and bovine serum albumin (BSA) on rat liver mitochondrial function and structure were studied by measuring oxygen uptake, 90° light-scattering, adenosine triphosphatase activity and pyridine nucleotides fluorescence. 1. The low concentration of oleate induced the uncoupling of oxidative phosphorylation and the scattering change of mitochondria. This action of oleate differed from that of oleate at a high concentration which induces the high amplitude swelling with respect to its physiological and biochemical properties. The degrees of reversal swelling (shrinkage) and of oxygen uptake induced by oleate in the presence of Pi and succinate were altered proportionately to the concentration of oleate, and the concentration of oleate to the shrinkage coincided with that of the maximal respiratory release. 2. Antimycin A or 2, 4- dinitrophenol prevented the oleate-induced mitochondrial shrinkage, but the treatment of these agents after prior incubation with Pi and succinate allowed the shrinkage, though the degree was small in its extent compared with that in the absence of inhibitors. On the other hand, oligomycin did not affect the shrinkage with oleate. 3. BSA protected the mitochondrial phosphorylation from the uncoupling action of oleate without showing any effect of its own. A complete reversal could readily be demonstrated by a sufficient amount of BSA from the uncoupling, structural changes, and oxidation of intramitochondrial pyridine nucleotides induced by oleate in a low concentration. 4. The oleate-stimulated latent ATPase activity was proportional to the oleate-induced shrinkage of mitochondria with respect to the concentration of oleate. The latent ATPase was abolished also by the addition of a sufficient amount of BSA. 5. The action of oleate on the phosphorylation sequence of mitochondria was discussed on the basis of the present findings.