scholarly journals The nature of the stimulation of the respiratory chain of rat liver mitochondria by glucagon pretreatment of animals

1982 ◽  
Vol 204 (1) ◽  
pp. 37-47 ◽  
Author(s):  
A P Halestrap
Keyword(s):  
Respiratory Chain ◽  
Electron Flow ◽  
Liver Mitochondria ◽  
Complex Iii ◽  
Secondary Site ◽  
Rat Liver Mitochondria ◽  
Succinate Oxidation ◽  
Q Cycle ◽  
Cytochromes C ◽  
Stimulation Of

1. Studies on the cytochrome spectra of liver mitochondria from control and glucagon-treated rats in State 4, State 3 and in the presence of uncoupler are reported. 2. The stimulation of electron flow between cytochromes c1 and c observed previously [Halestrap (1978) Biochem. J. 172, 399-405] was shown to be an artefact of Ca2+-induced swelling of mitochondria. 3. When precautions were taken to prevent such swelling, glucagon treatment was shown to enhance the reduction of cytochromes c, c1 and b558 in both State 3 and uncoupled conditions with either succinate or glutamate + malate as substrate. An increase in the reduction of cytochromes b562 and b566 was also seen in some, but not all, experiments. 4. In State 4 with succinate but not glutamate + malate as substrate, cytochromes c, c1, b558, b562 and b566 showed increased reduction. 5. Glucagon stimulated oxidation of duroquinol and palmitoylcarnitine by intact mitochondria and of NADH by disrupted mitochondria. 6. No effect of glucagon on succinate dehydrogenase activity or the temperature-dependence of succinate oxidation could be detected. 7. Glucagon enhanced the inhibition of the respiratory chain by colletotrichin, but not antimycin or 8-heptyl-4-hydroxyquinoline N-oxide. 8. These results are interpreted in terms of a primary stimulation by glucagon of the ‘Q cycle’ [Mitchell (1976) J. Theor. Biol. 62, 827-367] within Complex III (ubiquinol:cytochrome c oxidoreductase) and a secondary site of action involving stimulation of electron flow into Complex III from the ubiquinone pool. 9. Ageing of mitochondria, hyperosmotic treatment or addition of 20 mM-benzyl alcohol opposed the effects of glucagon treatment on cytochrome spectra and colletotrichin inhibition of respiration. 10. These results support the hypothesis that glucagon exerts its effects on the mitochondria by perturbing the membrane structure.

scholarly journals Stimulation of the respiratory chain of rat liver mitochondria between cytochrome c1 and cytochrome c by glucagon treatment of rats

1978 ◽  
Vol 172 (3) ◽  
pp. 399-405 ◽  
Author(s):  
Andrew P. Halestrap
Keyword(s):  
Cytochrome C ◽  
Cytochrome B ◽  
Respiratory Chain ◽  
Redox State ◽  
Electron Flow ◽  
Rat Liver Mitochondria ◽  
O2 Uptake ◽  
Pyruvate Metabolism ◽  
Cytochromes C ◽  
Cytochrome C1

Mitochondria from glucagon-treated rats oxidize succinate, but not ascorbate plus tetramethylphenylenediamine, faster in the uncoupled state than do control mitochondria. The rate of O2 uptake in the presence of both substrates is equal to the sum of the rates of the O2 uptake in the presence of either substrate alone. It is concluded that the mitochondrial respiratory chain is limited at some point between cytochromes b and c and that this step is regulated by glucagon. Measurement of the cytochrome spectra under uncoupled conditions in the presence of succinate and rotenone demonstrates a crossover between cytochromes c and c1 when control mitochondria are compared with those from glucagon-treated rats, cytochrome c being more oxidized and cytochrome c1 more reduced in control mitochondria. Under conditions where pyruvate metabolism is studied the control mitochondria are generally more oxidized than those from glucagon-treated rats, the redox state of cytochrome b-566 correlating with the rate of pyruvate metabolism in sucrose medium. However, when the redox state of the mitochondria is taken into account, a crossover between cytochromes c and c1 is again apparent. The spectra of the b cytochromes are complex, but cytochrome b-562 appears to become more reduced relative to cytochrome b-566 in mitochondria from glucagon-treated rats than in control mitochondria. This can be explained by the existence of a more alkaline matrix in glucagon-treated rats, the redox potential for cytochrome b being pH-sensitive. It is concluded that glucagon stimulates electron flow between cytochromes c1 and c. The physiological significance of these findings is discussed.

scholarly journals Evidence of a phosphate-transporter system in the inner membrane of isolated mitochondria

1969 ◽  
Vol 111 (5) ◽  
pp. 665-678 ◽  
Author(s):  
D. D. Tyler
Keyword(s):  
Respiratory Chain ◽  
Rat Liver ◽  
Inorganic Phosphate ◽  
Ammonium Phosphate ◽  
Atp Synthesis ◽  
Liver Mitochondria ◽  
Phosphate Transporter ◽  
Rat Liver Mitochondria ◽  
Succinate Oxidation ◽  
Inner Membrane

1. The organic mercurial sodium mersalyl, formaldehyde, dicyclohexylcarbodiimide and tributyltin each blocked respiratory-chain-linked ATP synthesis in rat liver mitochondria. 2. Mersalyl and formaldehyde also blocked a number of other processes dependent on the entry of inorganic phosphate into mitochondria, including mitochondrial respiration and swelling stimulated by cations and phosphate, the substrate-level phosphorylation reaction of the citric acid cycle, and swelling in ammonium phosphate. 3. Dicyclohexylcarbodi-imide and tributyltin did not inhibit the entry of phosphate into mitochondria. 4. Mersalyl and formaldehyde had a relatively slight effect on succinate oxidation and swelling stimulated by cations when phosphate was replaced by acetate, on succinate oxidation stimulated by uncoupling agents, and on swelling in solutions of ammonium salts other than phosphate or arsenate. 5. Formaldehyde blocked the oxidation of NAD-linked substrates in mitochondria treated with 2,4-dinitrophenol and the ATP-dependent reduction of NAD by succinate catalysed by ox heart submitochondrial particles. Both these effects appear to be due to an inhibition by formaldehyde of the NAD–flavin region of the respiratory chain. 6. Concentrations of dicyclohexylcarbodiimide or tributyltin sufficient to abolish ADP-stimulated respiration blocked the dinitrophenol-stimulated adenosine triphosphatase activity, whereas mersalyl and formaldehyde caused only partial inhibition of ATP hydrolysis. 7. When mitochondria were incubated with dinitrophenol and ATP, less than 10% of the total inorganic phosphate liberated was recovered in the mitochondria and no swelling occurred. In the presence of mersalyl or formaldehyde at least 80% of the total inorganic phosphate liberated was retained in the mitochondria and extensive swelling was observed. This swelling was inhibited by oligomycin but not by antimycin or rotenone. 8. The addition of mersalyl to mitochondria swollen by treatment with valinomycin, K+ and phosphate blocked the contraction induced by dinitrophenol and caused an increase in the phosphate content of the mitochondria, but had no effect on the contraction of mitochondria when phosphate was replaced by acetate. 9. It is concluded that mitochondria contain a phosphate-transporter system, which catalyses the movement of phosphate in either direction across the mitochondrial membrane, and that this system is inactivated by organic mercurials and by formaldehyde. Evidence is presented that the phosphate-transporter system is situated in the inner membrane of rat liver mitochondria and is also present in other types of mammalian mitochondria.

Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

1971 ◽  
Vol 29 ◽  
pp. 570-571
Author(s):  
E. A. Elfont ◽  
R. B. Tobin ◽  
D. G. Colton ◽  
M. A. Mehlman
Keyword(s):  
Chemical Composition ◽  
Rat Liver ◽  
Future Study ◽  
Mode Of Action ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Effective Inhibitor ◽  
Biochemical Effects ◽  
Glycerophosphate Dehydrogenase ◽  
Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

Mitochondrial function in flying honeybees (Apis mellifera): respiratory chain enzymes and electron flow from complex III to oxygen

2000 ◽  
Vol 203 (5) ◽  
pp. 905-911 ◽  
Author(s):  
R.K. Suarez ◽  
J.F. Staples ◽  
J.R. Lighton ◽  
O. Mathieu-Costello
Keyword(s):  
Surface Area ◽  
Muscle Mass ◽  
Respiratory Chain ◽  
Mitochondrial Function ◽  
Electron Flow ◽  
Complex Iii ◽  
High Mass ◽  
Metabolic Rates ◽  
Turnover Rates ◽  
Respiratory Enzymes

The biochemical bases for the high mass-specific metabolic rates of flying insects remain poorly understood. To gain insights into mitochondrial function during flight, metabolic rates of individual flying honeybees were measured using respirometry, and their thoracic muscles were fixed for electron microscopy. Mitochondrial volume densities and cristae surface densities, combined with biochemical data concerning cytochrome content per unit mass, were used to estimate respiratory chain enzyme densities per unit cristae surface area. Despite the high content of respiratory enzymes per unit muscle mass, these are accommodated by abundant mitochondria and high cristae surface densities such that enzyme densities per unit cristae surface area are similar to those found in mammalian muscle and liver. These results support the idea that a unit area of mitochondrial inner membrane constitutes an invariant structural unit. Rates of O(2) consumption per unit cristae surface area are much higher than those estimated in mammals as a consequence of higher enzyme turnover rates (electron transfer rates per enzyme molecule) during flight. Cytochrome c oxidase, in particular, operates close to its maximum catalytic capacity (k(cat)). Thus, high flux rates are achieved via (i) high respiratory enzyme content per unit muscle mass and (ii) the operation of these enzymes at high fractional velocities.

Oxidative energy metabolism in germ-free and conventional rat liver mitochondria

1975 ◽  
Vol 228 (2) ◽  
pp. 526-529 ◽  
Author(s):  
DL Sewell ◽  
BS Wostmann ◽  
C Gairola ◽  
MI Aleem
Keyword(s):  
Wistar Rats ◽  
Liver Mitochondria ◽  
The State ◽  
Rat Liver Mitochondria ◽  
Succinate Oxidation ◽  
Germ Free ◽  
Adult Rat ◽  
Respiration Rates ◽  
Oxidative Energy Metabolism ◽  
Beta Hydroxybutyrate

The ADP:O ratios and State 3 (ADP-stimulated) and State 4 (controlled) rates of succinate, beta-hydroxybutyrate, isocitrate, glutamate, pyruvate + malate, alpha-ketoglutarate, and ascorbate + N,N,N',N'-tetramethylphenylenediamine (TMPD) oxidation were examined in liver mitochondria from germ-free and conventional rats of both Lobund Wistar (100-day-old) and Fisher (120-day-old) strains. The State 3 respiration rates of isolated mitochondria from germ-free and conventional rats were comparable except for the rate of succinate oxidation in the Wistar rats, which was significantly lower (approx. 10%). The State 4 respiration rates were generally lower in mitochondria isolated from germ-free Fisher rats (approx. 8%) and significantly lower (approx. 18%) in germ-free Wistar rats. The ADP:O ratios were similar in germ-free and conventional rats. Serum thyroxine concentrations indicated delayed maturation of thyroid function in young germ-free rats, but adult animals had concentrations similar to those found in conventional rats. The results indicate that, although absence of a microflora results in a 20-30% reduction in metabolic rate, the germ-free state has little influence on the functional respiration or oxidative phosphorylation of mitochondria isolated from the liver of the adult rat.

The polyphasic nature of the respiratory process at the mitochondrial level

1990 ◽  
Vol 258 (3) ◽  
pp. C504-C511 ◽  
Author(s):  
B. D. Reynafarje ◽  
P. W. Davies
Keyword(s):  
Oxygen Consumption ◽  
Energy Demand ◽  
Initial Conditions ◽  
Electron Flow ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Second Phase ◽  
Third Phase ◽  
Metabolic Conditions ◽  
Kinetics Of

The kinetics of oxygen consumption by rat liver mitochondria, respiring under a variety of metabolic conditions, have been studied. Respiration was initiated by injecting oxygen into anaerobic suspensions of mitochondria. It was found that, irrespective of the metabolic state of the mitochondria and the nature of the respiratory substrate, the rates of electron flow and oxygen consumption follow the pattern of a polyphasic reaction. The rates of oxygen uptake during the first phase are extremely fast and depend on oxygen concentration. The second phase represents a transition in which net oxidation of cytochrome-c oxidase stops and the rates of oxygen consumption suddenly decrease. The third phase is characterized by its changeability. Depending on initial conditions the rates may increase, decrease, or remain constant, although the reaction is not one of zero order. During the last phase, the rates decrease and the oxidase becomes increasingly reduced. It is postulated that the mitochondrial respiratory process is basically a cyclic event in which the redox state of the membrane and the rates of oxygen consumption oscillate with amplitudes and frequencies conditioned by the energy demand and energy-yielding capacity of the cell.

The inhibition of mammalian mitochondrial NADU oxidation by chloramphenicol and its isomers and analogues

1968 ◽  
Vol 46 (9) ◽  
pp. 1003-1008 ◽  
Author(s):  
K. B. Freeman ◽  
D. Haldar
Keyword(s):  
Cytochrome B ◽  
Respiratory Chain ◽  
Rat Liver ◽  
Nadh Dehydrogenase ◽  
Coenzyme Q ◽  
Liver Mitochondria ◽  
Heart Mitochondria ◽  
Rat Liver Mitochondria ◽  
Beef Heart ◽  
Beef Heart Mitochondria

Chloramphenicol and its isomers and analogues have been found to inhibit the oxidation of NADH, but not that of succinate, by beef heart mitochondria. They must therefore inhibit the NADH dehydrogenase segment of the respiratory chain. Chloramphenicol gave 50% inhibition at a concentration of 1 mM. The methylthio analogue of chloramphenicol inhibited NADH – coenzyme Q6 reductase but not NADH–ferricyanide reductase. Spectrophotometric observations suggest that these inhibitors act between NADH and flavin in coupled rat liver mitochondria and between flavin and cytochrome b in uncoupled beef heart mitochondria.

Inhibition of Succinic Dehydrogenase and F0F1-ATP Synthase by 4,4'-Diisothiocyanatostilbene-2,2'-disulfonic Acid (DIDS)

1997 ◽  
Vol 52 (11-12) ◽  
pp. 799-806 ◽  
Author(s):  
Celene F. Bernardes ◽  
Jose R. Meyer-Fernandes ◽  
Orlando B. Martins ◽  
Anibal E. Vercesi
Keyword(s):  
Succinic Dehydrogenase ◽  
Atp Synthesis ◽  
Liver Mitochondria ◽  
Disulfonic Acid ◽  
Rat Liver Mitochondria ◽  
Dependent Manner ◽  
Submitochondrial Particles ◽  
Succinate Oxidation ◽  
Hydrolytic Activities ◽  
Dose Dependent

Abstract This study shows that incubation of rat liver mitochondria in the presence of the thiol/ amino reagent 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DID S) is followed by inhibition of both succinate supported respiration and oxidative phosphorylation. Half-maximal inhibition of succinic dehydrogenase activity and succinate oxidation by mitochondria was attained at 55.3 and 60.8 μm DIDS, respectively. DIDS did inhibit the net ATP synthesis and ATP ⇔ [32P]Pi exchange reaction catalyzed by submitochondrial particles in a dose-dependent manner (Ki= 31.7 μm and Ki = 32.7 μm), respectively. The hydrolytic activities of uncoupled heart submitochondrial particles and purified F 1 -ATPase were also inhibited 50% by 31.9 and 20.9 μm DIDS, respectively.

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