Activity Of Rat Liver Mitochondria Research Articles

The effect of p,p′-DDT (Dicophane) and its metabolites on ATPase activity in rat liver mitochondria

The effect of DDT and its main metabolites on ATPase activity in rat liver mitochondria was studied. These compounds stimulated ATPase activity in intact mitochondria of rat liver and had no effect on ATPase activity in damaged mitochondria. This suggests that the uncoupling of the oxidative phosphorylation in mitochondria may be responsible for the toxic effect of DDT in mammals.

Tetradifon: An oligomycin-like inhibitor of energy-linked activities of rat liver mitochondria

Tetradifon (p-chlorophenyl-2,4,5-trichlorophenyl sulfone) at concentrations between 4.5 and 27.0 nmoles/mg mitochondrial protein provides half-maximal inhibition of the following energy-linked activities of rat liver mitochondria: ADP-stimulated respiration, DNP-stimulated ATPase activity, Mg ++-stimulated ATPase activity, and P i-ATP exchange activity. Tetradifon has no effect on the activity of soluble ATPase purified from rat liver mitochondria. Respiration inhibited by tetradifon is restored upon addition of 2,4-dinitrophenol. It is concluded that tetradifon acts at or near the oligomycin sensitivity conferring complex located in the mitochondrial inner membrane.

Osmotic pressure and ATPase activity of rat liver mitochondria

The effect of increasing concentrations of electrolytes and nonelectrolytes on the ATPase activity of rat liver mitochondria was studied. It was found that as the molarity of nonpenetrating solutes was increased above isotonicity the ATPase activity induced by 2,4-dinitrophenol, pentachlorophenol, valinomycin, and gramicidin sharply decreased. The inhibitory effect of nonpenetrating solutes could be released by the addition of permeant salts. It is suggested that the inhibition of ATPase activity by impermeant solutes at high concentrations is due to the loss of water from the matrix space.

Inhibited respiration and ATPase activity of rat liver mitochondria under conditions of matrix condensation

Inhibited respiration and ATPase activity of rat liver mitochondria under conditions of matrix condensation

STUDIES ON MONOAMINE OXIDASE (REPORT 17) EFFECTS OF NaNO2 ON MAO FROM RAT LIVER MITOCHONDRIA

There have been few reports on monoamine oxidase (MAO) [EC 1.4.3.4. monoamine: oxygen oxidoreductase (deaminating)] activators and at present it is only known that reserpine (1-3), in vivo and 4-diazo-imidazole-5-carboxamide (4), in vitro cause increase in MAO activity. A previous report from this laboratory showed that sodium nitrite (NaNO2) activated MAO with certain substrates (5). Namely, using benzylamine, butylamine, amylamine, hexylamine or β-phenylethylamine as substrate, MAO activity in rat liver mitochondria was increased by NaNO2, while when using tyramine or serotonin it was inhibited. In rat brain mitochondria, MAO activity was increased by NaNO2 when tyramine or butylamine were used as substrates, however, it was inhibited when other substrates were used. These results suggested the presence of multiple forms of MAO in mitochondria. This paper describes the effects of NaNO2 on the substrate specificities, pS maxima, pH optima and Michaelis constants of MAO in rat liver mitochondria.

Formation of lipid peroxide in rat liver mitochondria. I

1) In vitro experiment was made to clarify the interrelationship among lipid peroxidation, lipid compositions, and cytochrome oxidase activity in rat liver mitochondria. 2) Ascorbic acid and metal ions (Fe2+, Fe3+, Cu2+) catalysed lipid peroxidation in mitochondria, but Ca2+ inhibited it. 3) Combined application of ascorbic acid with Fe2+ (or Fe3+) markedly, increased the formation of lipid peroxide in mitochondria but that of ascorbic acid with Ca2+ or Cu2+ did not. 4) Linoleic acid and LAHPO did not affect the peroxidation process in liver mitochondria, in vivo or in vitro. 5) Lipid peroxidation in vitro promoted by ascorbic acid and Fe2+ was accompanied by the decrease of cytochrome oxidase activity and unsaturated fatty acid (C18 : 2, C20 : 4, C22 : 6) content of mitochondria. Among the fatty acid compositions of phosphatidylserine and phosphatidylinositol, diminution of linoleic acid and arachidonic acid was predominant. 6) Relationship among lipid compositions, lipid peroxidation, and cytochrome oxidase activity in rat liver mitochndria was discussed.

Effect of Δ l-tetrahydrocannabinol on ATPase activity of rat liver mitochondria

Effect of Δ l-tetrahydrocannabinol on ATPase activity of rat liver mitochondria

Influence of a Low Casein Diet on Malate Dehydrogenase Activity of Rat Liver Mitochondria and Homogenate Disrupted by Various Treatments

It has been shown previously in this laboratory that the structure of rat liver mitochondria was changed by a low casein diet. In the present experiments, by measuring malate dehydrogenase activity, the degree of disruption by various destructive treatments on liver mitochondria from rats fed a low casein diet was investigated. The low casein diet contained 4% casein, and the control diet, 25%. Mitochondrial structure was disrupted by three methods: dilution with water, sonic disintegration, and addition of Triton X-100. Malate dehydrogenase activity per milligram of mitochondrial protein was higher in rats fed the low casein diet when the mitochondrial structure was disrupted by dilution with water and by addition of Triton X-100. However, when it was disrupted by sonic disintegration, the activity was almost the same in rats in both diet groups.

Dual localization and properties of ATP-dependent long-chain fatty acid activation in rat liver mitochondria and the consequences for fatty acid oxidation

1. Direct evidence is given for the existence of two ATP-dependent palmitoyl-CoA synthesizing enzymes, localized in different compartments of the rat-liver mitochondrion. 2. About 90% of the total activity of rat liver mitochondria is localized in the mitochondrial outer membrane and about 10% in the inner membrane-matrix compartment. 3. The two enzyme systems show different apparent K m 's for fatty acid and ATP, and different apparent K i 's for AMP and adenosine. 4. The inner membrane-matrix enzyme, in contrast to the outer membrane and the microsomal enzyme, is strongly inhibited by octanoate. 5. Comparison of the kinetics of the two ATP-dependent long-chain fatty acid-activating enzymes with the kinetics of long-chain fatty acid oxidation shows, that during fatty acid oxidation at low concentrations of palmitate or oleate, in the presence of carnitine, the outer membrane acyl-CoA synthetase is operating. In the absence of carnitine and at high concentrations of long-chain fatty acids the activation reaction occurs in the inner membrane-matrix compartment of the mitochondrion. 6. The long-chain fatty acid concentration needed for half-maximal velocity of fatty acid oxidation by isolated rat liver mitochondria is about 1 μM in the presence of carnitine and 100–200 μM in the absence of carnitine.

In vivo cortisol action on RNA synthesis in rat liver nuclei and mitochondria.

VARIOUS mechanisms have been proposed for the action of hormones in cells. One is a cytoplasmic mechanism involving mitochondria1,2; a second implies that cytoplasmic protein receptors act as sites3 for the hormone action; a third proposes that the nuclei act as a primary site for hormone action4,5. We now demonstrate that cortisol, when used for brief periods and in physiological doses, increased the RNA polymerase activity of rat liver mitochondria. In these conditions nuclear RNA synthesis was not affected. Hormone treatment for longer periods or treatment with large doses for short time periods increased the nuclear RNA polymerase activity and suppressed the mitochondrial enzyme.

Carnitine palmitoyltransferase activities (EC 2.3.1.-) of rat liver mitochondria.

1. A continuously recording and sensitive fluorimetric assay is described for carnitine palmitoyltransferase. This assay has been applied to whole or disintegrated mitochondria and to soluble protein fractions. 2. When rat liver mitochondria had been disintegrated by ultrasound, the specific activity of carnitine palmitoyltransferase was 15-20m-units/mg of protein. Only one-fifth of this activity was assayable (with added substrates) before mitochondrial disintegration. 3. It is concluded that there are two carnitine palmitoyltransferase activities in rat liver mitochondria, of which one (type I) is relatively superficial in location and catalyses an acyl-group transfer between added CoA and carnitine, whereas the other (type II) is less superficial and catalyses an acyl-group transfer in unbroken mitochondria between added carnitine and intramitochondrial CoA. The existence of two distinct carnitine palmitoyltransferases was predicted by Fritz & Yue (1963). 4. In unbroken mitochondria, type I transferase is accessible to the inhibitor 2-bromostearoyl-CoA whereas the type II transferase is inaccessible. 5. A major part of the total carnitine palmitoyltransferase activity of rat liver mitochondria is membrane-bound and of type II. 6. These observations, when considered in conjunction with the penetration of mitochondria by CoASH or carnitine, indicate that the type II transferase is attached to the inner mitochondrial membrane.

Growth inhibitory action of saccharin and cyclamate on rats receiving a poor rice diet.

1. The effect of saccharin and cyclamate on growth of young rats fed on a poor rice diet or a balanced diet was investigated.2. Saccharin and cyclamate retarded the growth of rats on the multi-deficient diet but not of those on the well-balanced diet during an 8-week feeding period.3. The sweeteners did not produce any macroscopic or microscopic changes in the liver, kidneys, intestines, spleen or lungs of the animals receiving the poor rice diet other than the changes resulting from the nutritional deficiency of the diet.4. The sweeteners did not inhibit the liver xanthine oxidase activity of rats receiving the poor rice diet to an extent greater than the inhibition brought about by the deficiency of protein in the diet.5. When given by intubation to healthy rats, the sweeteners inhibited the induction of liver tryptophan oxygenase; given in vitro, they inhibited the succinate dehydrogenase activity of rat liver mitochondria.

The localization of proteolytic activity in rat liver mitochondria and its relation to mitochondrial swelling and aging.

1. On storage of rat liver mitochondria at 0 degrees , water content, total amino acid content and leakage of protein all rose steadily over a 72hr. period. The initial ratio of intramitochondrial to extramitochondrial amino acid concentration lay between 18 and 24. Initially this rose, but it then fell to 1.9 at the end of storage. The concentration gradient between internal and external amino acids was relatively constant throughout the period. These processes were accentuated at 22 degrees and 40 degrees , the concentration gradient reaching 70mumoles/ml., water content rising to 8.3mg./mg. dry wt. and protein leakage reaching 42% of total mitochondrial protein. ;Swelling agents' produced no correlated changes in amino acid production and swelling. 2. Added glutamate was not concentrated within the pellet of whole or disrupted mitochondria. Endogenous amino acids were distributed evenly between the pellet and the supernatant of disrupted mitochondria. It is concluded that amino acids are produced within mitochondria and that adsorption and uptake from the medium do not contribute significantly to amino acids in the pellet. 3. beta-Glycerophosphate, a lysosome protectant, increased amino acid production by rat liver mitochondria. Treatment with Triton X-100 and disruption by freezing and thawing showed that 56% of proteolytic activity was ;free' in whole mitochondria, whereas only 11% of acid phosphatase activity, a lysosomal enzyme, was ;free'. 4. ;Light' mitochondria contained 30% more neutral proteolytic activity but 300% more acid phosphatase activity than ;heavy' mitochondria. 5. Electron micrographs of mitochondrial preparations showed less than one particle in 500 that could be identified as a lysosome. Treatment with Triton X-100 disrupted the structure of roughly 50% of the mitochondria; the rest appeared to retain their membrane, cristae and ground substance. Freezing and thawing caused gross swelling and loss of ground substance and rupture of external membranes. 6. Of the recovered proteolytic activity, 81% at pH7.4 and 70% at pH5.8 were found in the high-speed supernatant of broken mitochondria. A further fivefold increase in specific activity was found in the first protein fraction obtained by Sephadex G-50 gel filtration. 7. Between 60 and 80% of proteolytic activity was found in the 40-60%-saturated ammonium sulphate precipitate. Almost all of the soluble-fraction proteolytic activity could be recovered in a pH5.0 supernatant. 8. The results give no support to the view that mitochondrial neutral proteolytic activity reflects lysosomal content. 9. The possible role of intramitochondrial amino acid production and the proteolysis of internal barriers in passive swelling of mitochondria is discussed.

Dietary induced alterations in swelling characteristics and endogenous phospholipase A2 activity of rat liver mitochondria

The present study describes the rapid alterations in the fatty acid patterns of phosphatidyl choline and phosphatidyl ethanolamine from rat liver mitochondria induced by corn oil feeding to EFA-deficient rats. Simultaneous changes occurring with comparable rates were observed in the swelling properties and phospholipase A(2) activity of the mitochondria. Mitochondria isolated from the liver of EFA-deficient rats exhibited a high tendency to swell and a high phospholipase A(2) activity in comparison with those prepared from normal rat liver. Feeding of corn oil for 48 hr to the EFA-deficient rats completely reduced this high rate of swelling and phospholipase A(2) activity to the normal level. In the same time eicosatrienoic acid, a characteristic fatty acid constituent of phospholipids from EFA-deficient animals, was replaced by the more common fatty acids, linoleic and arachidonic. The possible relationship between fatty acid constituents of phospholipids, swelling properties and phospholipase A(2) activity in rat liver mitochondria are discussed.

Localization of oligomycin-sensitive ADP-ATP exchange activity in rat liver mitochondria

Intact rat liver mitochondria catalyze an ADP-ATP exchange which is partially inhibited by oligomycin and dinitrophenol ( Wadkins and Lehninger, 1963; Guillory and Slater, 1965). It has been postulated that the dinitrophenol- and oligomycin-sensitive ADP-ATP exchange reaction is catalyzed by the enzyme(s) participating in ATP formation during oxidative phosphorylation ( Wadkins and Lehninger, 1958; 1963). However, the presence of large amounts of adenylate kinase and nucleoside diphosphokinase, which catalyze oligomycin-insensitive ADP-ATP exchanges, has rendered further investigation of the oligomycin-sensitive exchange difficult. In this communication it is shown that when rat liver mitochondria are fractionated with digitonin the oligomycin-sensitive ADP-ATP exchange activity is recovered with the inner membrane-matrix fraction, while all of the nucleoside diphosphokinase and adenylate kinase activity is released with the outer membrane. The exchange activity found in the inner membrane-matrix fraction is localized in the inner membrane and is completely inhibited by oligomycin, dinitrophenol, and atractyloside when assayed in the absence of added Mg ++. Thus, the oligomycin-sensitive ADP-ATP exchange activity observed in intact mitochondria does not appear to be catalyzed by nucleoside diphosphokinase or adenylate kinase.

Monovalent cations and mitochondrial ATPase activity.

The effect of monovalent cations on the ATPase activity of rat liver mitochondria was studied.It was found that alkali-metal ions can activate ATPase when mitochondria become permeable to them by treatment with surface-active agents such as Triton-X-100, alcohols, valinomycin, gramicidin, 2,4-dinitrophenol.The alteration of mitochondrial permeability produced by progressive acidification of the incubation medium indicates that the ability of alkali-metal ions to penetrate mitochondria increases in the order: Li+, Na+, K+, Rb+, and Cs+, which is the order of the decreasing hydrated ionic radii.The results obtained in the presence of valinomycin or gramicidin were comparable with those reported by other workers for the exchange cation–H+. A Na+-activated ATPase could be observed in the presence of high concentrations of valinomycin.The action of surface-active agents on ATPase activity was dependent upon the presence of monovalent cations.It is concluded that control of the metabolism of mitochondria can be exerted through changes in their permeability to cations present in the extramitochondrial cytoplasm.

Phospholipase activity in rat liver mitochondria studied by the use of endogenous substrates

The hydrolysis of endogenous phosphatidyl ethanolamine and lecithin in rat liver mitochondria has been studied by using mitochondria from rats injected with ethanolamine-1,2-(14)C or choline-1,2-(14)C. A phospholipase A-like enzyme has been demonstrated, which catalyzes the hydrolysis of one fatty acid ester linkage in phosphatidyl ethanolamine and lecithin. Phosphatidyl ethanolamine is hydrolyzed in preference to lecithin and the main reaction products are free fatty acids and lysophosphatidyl ethanolamine. The further breakdown of lysophospholipids appears to be limited in mitochondria, which indicates that lysophospholipase activity is mainly located extramitochondrially. The enzymic system is greatly stimulated by calcium ions, and also slightly by magnesium ions, while EDTA inhibits it almost completely. These findings are discussed in relation to previous observations on the effect of calcium and of EDTA on the functions of mitochondria. The possible function of the mitochondrial phospholipase for the formation of phospholipids with special fatty acids at the alpha- and -position is discussed.

NOCTURNAL CHANGES IN OXIDATIVE ACTIVITIES OF RAT LIVER MITOCHONDRIA.

Male rats kept on an artificial day-night cycle were active at night and rested during the day. The rate of succinate oxidation in liver mitochondria from these animals was 40 percent greater at night. Significant nocturnal increases in the ratio of phosphate to oxygen were obtained with citrate, alpha-ketoglutarate, and malate.

Effect of sodium and potassium on mitochondrial adenosinetriphosphatase activity

The sensitivity to sodium and potassium of the adenosinetriphosphatase activity of rat liver mitochondria at various stages of degradation was studied. In intact mitochondria no differences could be detected in sodium or potassium chloride media; in the presence of gramicidin and 2,4-dinitrophenol, the behavior of the reaction was independent of the cationic environment. However, when the mitochondrial structure was disrupted or altered by deoxycholate or sonication, a significant greater activity was encountered in the potassium-containing tubes. The soluble enzyme extracted from mitochondrial acetone powders showed also a higher activity in potassium medium. The response of the adenosinetriphosphatase system to sodium and potassium seems to depend on the structural conditions of the mitochondria.

THE EFFECT OF ULTRAVIOLET LIGHT ON MITOCHONDRIA: VII. RESTORATION OF DINITROPHENOL-ACTIVATED ADENOSINETRIPHOSPHATASE BY VITAMIN K1 FOLLOWING INHIBITION BY FAR-ULTRAVIOLET LIGHT

The effect of ultraviolet light on enzyme activity in rat liver mitochondria was studed. Restoration of dinitrophenol-activated adenosinetriphosphatase by vitamin K following inhibition by far-ultraviolet light is reported. (C.H.)