An Endogenous Uncoupling and Swelling Agent in Liver Mitochondria and Its Enzymic Formation

Effect of ethanol on rat liver. 4. The influence of vitamins, electrolytes and amino acids on the structure and function of mitochondria from rats receiving ethanol

1. Feeding rats with a 15% ethanol solution for several weeks caused structural and functional changes in their liver mitochondria, although their intake of solid food was about the same as that of the controls.

2. Attempts were made to counteract these effects of ethanol by increasing the intake of amino acids, vitamins, lipotropic compounds and electrolytes beyond that which is adequate when water is the drinking fluid.

3. An increased intake of nicotinic acid, together with aqueous ethanol, caused a further enlargement of the mitochondria above that obtained with ethanol solution alone. the diluted matrix observed with the ethanol and nicotinic acid treatment suggested that water imbibition by the mitochondria caused this further enlargement.

4. In rats receiving ethanol fortified with magnesium sulphate and lipotropic compounds (choline, methionine) there was a further increase in mitochondrial size, as compared with those receiving ethanol alone. The matrix was, however, of the same density as in the mitochondria from the rats receiving ethanol alone. the oxidation rate of pyruvate and succinate was unchanged, but α-glycerophosphate and β-hydroxybutyrate were oxidized at a higher rate than in mitochondria from rats drinking ethanol or water.

5. When the ethanol solution was supplemented with amino acids (casein hydrolysate), vitamins and electrolytes, the mitochondrial enlargement after 120 days of treatment was less than with ethanol alone and was completely absent after 300 days. the oxidation rate of pyruvate and succinate was, however, not fully restored to normal.

Tissue culture and the study of anticancer agents

In a quest for potential antitumor agents, more than 100 fatty acids and their derivatives were tested against transplantable mouse tumors with both in vivo and in vitro methods. Three compounds, 2,3-decenoic acid, linoleic acid, and linolenic acid, were found to arrest the growth of three types of ascites tumor cells, while 2-nonenoic, 10-undecenoic, oleic, and arachidonic acids were effective to a varying degree. The cytotoxic effects of these unsaturated fatty acids on monolayer cultures of Ehrlich ascites tumor cells and of normal mouse embryos were evaluated in experiments in which graded concentrations of the test materials incorporated in the culture medium were used.

The direct action of CCL-4 on the metabolism of liver slices

The metabolism of glucose, galactose, leucine, acetate, and palmitate by rat liver slices incubated in the presence of varying amounts of CCl4was studied. Carbon tetrachloride, 1 to 9 μl, introduced into the side arm of a Warburg vessel, produced concentrations in the slices of 0.4 to 3.3 mg/g liver. At these concentrations the CCl4produced a decrease in C14O2production from succinate-2,3-C14and glucose-6-C14, but not from glucose-1-C14. The presence of CCl4did not appreciably affect CO2production from glucose-U-C14or galactose-1-C14but stimulated the incorporation of the monosaccharides into glycogen at the lower concentrations (1 mg CCl4/g liver). Higher concentrations of CCl4(2 mg/g liver) inhibited glycogen synthesis; the activities of glycogen synthetase and phosphorylase were decreased, but amylase activity and the level of glucose-6-phosphate in the liver slices remained unchanged. The oxidation of palmitate-1-C14and acetate-1-C14to C14O2is decreased at the higher concentrations of CCl4, while lipogenesis from acetate is stimulated by lower concentrations of CCl4. Esterification of palmitate is not affected by the presence of CCl4. It is concluded that the function of the tricarboxylic acid cycle is altered by CCl4and that acetate may be shunted into fatty acids. The oxidation of leucine-1-C14and the incorporation of the amino acid into protein were diminished in the presence of low concentrations of CCl4. These findings and the changes observed after CCl4administration in vivo are compared, and support is found for the view that CCl4affects hepatic metabolism in vivo directly.

PIGEON MUSCLE MITOCHONDRIA: ION CONCENTRATIONS, OXIDATIVE PHOSPHORYLATION, SWELLING, AND EXTRAPARTICULATE SPACE

Metabolically active mitochondria were isolated from pigeon breast muscle in cold 0.45 M sucrose with ATP, EDTA, and tris buffer at pH 7.4. Fresh mitochondria were analyzed for sodium, potassium, nitrogen, iron, and water. They were morphologically intact and showed respiratory control, respiration being limited by the phosphate acceptor and stimulated by dinitrophenol. The respiratory rate was the same in the Warburg respirometer as that in the polarograph chamber; no effect of agitation was observed. The rates of oxygen consumption over short periods of time were 30–40 μ atoms per hour per mg N for α-keto-glutarate and glutamate, 16 for malate, and 1.3 for β-OH butyrate; except in the last case, satisfactory P/O ratios were obtained. A soluble, heat-stable muscle factor, not precipitated at 100,000 × G, stimulated respiration with each substrate but did not affect phosphorylation. From optical density measurements of muscle mitochondria they appeared to behave as moderately good osmometers; only slight swelling occurred during oxidative phosphorylation, but this increased somewhat when respiration ceased. The osmotic dead space was estimated at 60% of the mitochondrial volume. With polyvinylpyrrolidone the extraparticulate space was found to be 27.8 ± 1.8%.

UNCOUPLING OF OXIDATIVE PHOSPHORYLATION BY IONIZING RADIATION: II. THE STABILITY OF MITOCHONDRIAL LIPIDS AND CYTOCHROMEc

Mitochondria isolated from the thymus of rats or rabbits 4 hours after 800 rads of ionizing radiation show uncoupling of their oxidative phosphorylation. There are no significant differences in the contents of phospholipids, neutral lipids, or total fatty acids between normal and uncoupled mitochondria. There was no evidence of the formation of any lipid uncoupling factor in thymus mitochondria from irradiated animals.Heart or liver mitochondria isolated from animals irradiated up to 12 hours previously showed no uncoupling of oxidative phosphorylation although preparations in various media could be made with reduced cytochrome c contents. No effect of irradiation upon endogenous cytochrome c or its binding in these mitochondria could be detected.Thymus mitochondria would appear to contain very low quantities of cytochrome c (less than 0.2 μg per mg protein), yet still be tightly coupled. It is suggested that this low level may indicate a critical condition at which radiation damage could become manifest.

PIGEON MUSCLE MITOCHONDRIA: ION CONCENTRATIONS, OXIDATIVE PHOSPHORYLATION, SWELLING, AND EXTRAPARTICULATE SPACE

Metabolically active mitochondria were isolated from pigeon breast muscle in cold 0.45 M sucrose with ATP, EDTA, and tris buffer at pH 7.4. Fresh mitochondria were analyzed for sodium, potassium, nitrogen, iron, and water. They were morphologically intact and showed respiratory control, respiration being limited by the phosphate acceptor and stimulated by dinitrophenol. The respiratory rate was the same in the Warburg respirometer as that in the polarograph chamber; no effect of agitation was observed. The rates of oxygen consumption over short periods of time were 30–40 μ atoms per hour per mg N for α-keto-glutarate and glutamate, 16 for malate, and 1.3 for β-OH butyrate; except in the last case, satisfactory P/O ratios were obtained. A soluble, heat-stable muscle factor, not precipitated at 100,000 × G, stimulated respiration with each substrate but did not affect phosphorylation. From optical density measurements of muscle mitochondria they appeared to behave as moderately good osmometers; only slight swelling occurred during oxidative phosphorylation, but this increased somewhat when respiration ceased. The osmotic dead space was estimated at 60% of the mitochondrial volume. With polyvinylpyrrolidone the extraparticulate space was found to be 27.8 ± 1.8%.