Acta Medica Okayama volume18 issue5

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.

For the purpose to reveal the mechanism of uptake and degradation of NAD by cells, the authors conducted the observation on the L cells cultured in the medium containing NAD and the following results have been obtained. 1. NAD in the medium is taken up by the cells in its intact form, reaching about twice the value of the control. 2. The spontaneously degraded products of NAD, nicotinamide and adenine dinucleotide ribose, in the same molar concentration as NAD used in the present experiment, have no effect on the NAD content of L cells. 3. The NAD taken up by the cells is degraded into nicotinamide mononucleotide (NMN) and adenine mononucleotide (AMP) by pyrophosphatase including NADpptase and excreted in the medium. Unexpectedly the ingested NAD is not degraded by NADase in the L cell. 4. L cells metabolize the same amount of NAD as that contained originally in the cell for about ten minutes, as calculated from the amount of NMN excreted in the medium.

An electon microscopic study on the structural differences among the red, white and intermediate muscle fibers of mice was made and the following results were obtained. 1. The red fiber contained very numerous mitochondria, the white fiber a few and the intermediate fiber a moderate number. The distribution of mitochondria was different in each type of muscle fiber. The cristae of mitochondria of the red fiber was quite well developed, that of the white fiber poorly and that of the intermedtate fiber moderately. 2. Sarcoplasmic reticulum of the white fiber was considerably well developed but that of the red and intermediate fibers poorly developed. 3. Glycogen particles were abundant in the white fiber, less in the intermediate fiber and least in the red fiber.

Respiration, activity of oleate oxidation and composition of the total fatty acids of rat liver were investigated in 3'-Me-DAB feeding. 1. Oxidative phosphorylation of rat liver mitochondria decreased temporarily at relatively earlier stages (about 2 to 3 weeks) in 3'-Me-DAB feeding. 2. The activity of oleate oxidation of rat liver mitochondria decreased rapidly to about one third of that in control groups after the start of 3'-Me-DAB feeding. 3. In the composition of the total fatty acids of rat liver, the proportion of oleic acid increased in 3'-Me-DAB groups. 4. Unknown octadecamonoenoic acid was observed in liver mitochondria of rat fed on 3'-Me-DAB. 5. Proportions of oleic and palmitoleic acids in liver tumors and mitochondria of liver tumors induced by 3'-Me-DAB feeding increased remarkably in contrast with decrease in those of palmitic and eicosapolyenoic acids. 6. A possibility was discussed about how higher level of oleate in the liver cells in azo dye feeding may be concerned with the tumor induction.