scholarly journals Transport of reduced nicotinamide–adenine dinucleotide into mitochondria of rat white adipose tissue

1970 ◽  
Vol 116 (2) ◽  
pp. 229-233 ◽  
Author(s):  
B. H. Robinson ◽  
M. L. Halperin
Keyword(s):  
Adipose Tissue ◽  
Rat Liver ◽  
White Adipose Tissue ◽  
Nicotinamide Adenine Dinucleotide ◽  
Aspartate Aminotransferase ◽  
Respiratory Control ◽  
Liver Mitochondria ◽  
Nadh Oxidation ◽  
Rat Liver Mitochondria ◽  
Reduced Nicotinamide Adenine Dinucleotide

Mitochondria from rat white adipose tissue were prepared, exhibiting good respiratory control and P/O ratios. They would not oxidize NADH unless NNN′N′-tetramethyl-p-phenylenediamine was added as a carrier of reducing equivalents. These mitochondria were found to oxidize neither l-glycerol 3-phosphate nor l-glutamate plus l-malate at significant rates. The activity of aspartate aminotransferase in these mitochondria was found to be low compared with that found in rat liver mitochondria. As a consequence of this, the adipose-tissue mitochondria exhibited very low rates of cytoplasmic NADH oxidation in a reconstituted Borst (1962) cycle compared with liver mitochondria.

scholarly journals Proton translocation coupled to quinone reduction by reduced nicotinamide–adenine dinucleotide in rat liver and ox heart mitochondria

1972 ◽  
Vol 130 (4) ◽  
pp. 1029-1044 ◽  
Author(s):  
H. G. Lawford ◽  
P. B. Garland
Keyword(s):  
Rat Liver ◽  
Nicotinamide Adenine Dinucleotide ◽  
Mitochondrial Membrane ◽  
Reductase Activity ◽  
Proton Translocation ◽  
Liver Mitochondria ◽  
Heart Mitochondria ◽  
Rat Liver Mitochondria ◽  
Quinone Reduction ◽  
Reduced Nicotinamide Adenine Dinucleotide

Measurements were made of the stoicheiometry of proton-translocation coupled to NAD(P)H oxidation by several quinones (duroquinone, ubiquinone0, ubiquinone1, ubiquinone2) in mitochondria from rat liver and ox heart. Observed stoicheiometries of protons translocated per mol of NADH oxidized (→H+/2e− ratios; Mitchell, 1966) ranged from 0.75 (rat liver mitochondria with ubiquinone1) to 1.55 (ox heart mitochondria with ubiquinone1 or ubiquinone2). Only the rotenone-sensitive pathway of NADH oxidation by quinone was able to support proton translocation. Correction of the observed →H+/2e− ratios for the loss of reducing equivalents to the rotenone-insensitive pathway increased their value to approx. 2.0. It is concluded that the rotenone-sensitive NADH– ubiquinone reductase activity of the respiratory chain may be organized in the mitochondrial membrane as a proton-translocating oxidoreduction loop. The number of such loops between NADH and ubiquinone is one, and not two, as initially proposed by Mitchell (1966).

THE ROLE OF MAGNESIUM IN THE OXIDATION OF EXTERNAL REDUCED NICOTINAMIDE ADENINE DINUCLEOTIDE BY RAT LIVER MITOCHONDRIA

1966 ◽  
Vol 44 (1) ◽  
pp. 67-76 ◽  
Author(s):  
Roberto Cereijo-Santaló
Keyword(s):  
Rat Liver ◽  
Nicotinamide Adenine Dinucleotide ◽  
Liver Mitochondria ◽  
Nadh Oxidation ◽  
Nicotinamide Adenine ◽  
Magnesium Concentration ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Releasing Effect ◽  
Isolated Rat

The oxidation of added dihydro-nicotinamide-adenine dinucleotide (NADH) by rat liver mitochondria in the presence of different concentrations of magnesium was studied.It was found that, in the absence of added magnesium, NADH was oxidized rapidly by isolated rat liver mitochondria. The addition of either magnesium or ATP strongly inhibited the oxidation of NADH.The inhibition of NADH oxidation induced by magnesium was not released by the addition of a phosphate acceptor, but it was partially released by the addition of ATP at concentrations lower than that of magnesium. As the concentration of ATP increased over that of magnesium, its releasing effect tended to disappear.Similarly, the inhibition of NADH oxidation induced by ATP was partially released by the addition of magnesium at concentrations lower than that of ATP. As the magnesium concentration increased over that of ATP, its releasing effect diminished and eventually caused a greater inhibition than that produced by ATP alone.It is suggested that conditions similar to those described in the oxidation of added NADH by isolated rat liver mitochondria might also occur in the intact cell.

scholarly journals Oxidative phosphorylation. The specific binding of trimethyltin and triethyltin to rat liver mitochondria

1970 ◽  
Vol 118 (1) ◽  
pp. 171-179 ◽  
Author(s):  
W. N. Aldridge ◽  
B. W. Street
Keyword(s):  
Adipose Tissue ◽  
Oxidative Phosphorylation ◽  
Brown Adipose Tissue ◽  
Binding Site ◽  
Rat Liver ◽  
Specific Binding ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Affinity Constants ◽  
Brown Adipose

1. The binding of trimethyltin and triethyltin to rat liver mitochondria was determined and the results were analysed by the method of Scatchard (1949). 2. One binding site (site 1) has the correct characteristics for the site to which trimethyltin and triethyltin are attached when they inhibit oxidative phosphorylation. For each compound the concentration of site 1 is 0.8nmol/mg of protein and the ratios of their affinity constants are the same as the ratio of the concentrations inhibiting oxidative phosphorylation. 3. Binding site 1 is present in a fraction derived from mitochondria containing only 15% of the original protein. In this preparation ultrasonication rapidly destroyed site 1. 4. Dimethyltin and diethyltin do not prevent binding of triethyltin to rat liver mitochondria, whereas triethyl-lead does. 5. Trimethyltin and triethyltin bind to mitochondria from brown adipose tissue and the results indicate a binding site 1 similar to that in rat liver mitochondria. 6. The advantages and limitations of this approach to the study of inhibitors are discussed.

scholarly journals The maturation of the inner membrane of foetal rat liver mitochondria. An example of a positive-feedback mechanism

1975 ◽  
Vol 150 (3) ◽  
pp. 477-488 ◽  
Author(s):  
J K Pollak
Keyword(s):  
Oxidative Phosphorylation ◽  
Rat Liver ◽  
Mitochondrial Membrane ◽  
Respiratory Control ◽  
Liver Mitochondria ◽  
Neonatal Rat ◽  
Rat Liver Mitochondria ◽  
Inner Mitochondrial Membrane ◽  
Mature Adult ◽  
Foetal Rat

A new method was devised for the isolation of foetal and neonatal rat lvier mitochondria, giving higher yields than conventional methods. 2. During development from the perinatal period to the mature adult, the ratio of cytochrome oxidase/succinate-cytochrome c reductase changes. 3. The inner mitochondrial membrane of foetal liver mitochondria possesses virtually no osmotic activity; the permeability to sucrose decreases with increasing developmental age. 4. Foetal rat liver mitochondria possess only marginal respiratory control and do not maintain Ca2+-induced respiration; they also swell in respiratory-control medium in the absence of substrate. ATP enhances respiratory control and prevents swelling, adenylyl imidodiphosphate, ATP+atractyloside enhance the R.C.I. (respiratory control index), Ca2+-induced respiratory control and prevent swelling, whereas GTP and low concentrations of ADP have none of these actions. It is concluded that the effect of ATP depends on steric interaction with the inner mitochondrial membrane. 5. When 1-day pre-partum foetuses are obtained by Caesarean section and maintained in a Humidicrib for 90 min, mitochondrial maturation is ‘triggered’, so that their R.C.I. is enhanced and no ATP is required to support Ca2+-dependent respiratory control or to inhibit mitochondrial swelling. 6. It is concluded that foetal rat liver mitochondria in utero do not respire, although they are capable of oxidative phosphorylation in spite of their low R.C.I. The different environmental conditions which the neonatal rat encounters ex utero enable the hepatic mitochondria to produce ATP, which interacts with the inner mitochondrial membrane to enhance oxidative phosphorylation by an autocatalytic mechanism.

scholarly journals Immunochemical studies with soluble and mitochondrial pyruvate carboxylase activities from rat tissues

1970 ◽  
Vol 119 (4) ◽  
pp. 735-742 ◽  
Author(s):  
F. J. Ballard ◽  
R. W. Hanson ◽  
Lea Reshef
Keyword(s):  
Adipose Tissue ◽  
Mammary Gland ◽  
Brown Adipose Tissue ◽  
Rat Liver ◽  
White Adipose Tissue ◽  
Pyruvate Carboxylase ◽  
Specific Activity ◽  
Rat Liver Mitochondria ◽  
Rat Tissues ◽  
Brown Adipose

1. Pyruvate carboxylase (EC 6.4.1.1), purified from rat liver mitochondria to a specific activity of 14 units/mg, was used for the preparation of antibodies in rabbits. 2. Tissue distribution studies showed that pyruvate carboxylase was present in all rat tissues that were tested, with considerable activities both in gluconeogenic tissues such as liver and kidney and in tissues with high rates of lipogenesis such as white adipose tissue, brown adipose tissue, adrenal gland and lactating mammary gland. 3. Immunochemical titration experiments with the specific antibodies showed no differences between the inactivation of pyruvate carboxylase from mitochondrial or soluble fractions of liver, kidney, mammary gland, brown adipose tissue or white adipose tissue. 4. The antibodies were relatively less effective in reactions against pyruvate carboxylase from sheep liver than against the enzyme from rat tissues. 5. Pyruvate carboxylase antibodies did not inactivate either propionyl-CoA carboxylase or acetyl-CoA carboxylase from rat liver. 6. It is concluded that pyruvate carboxylase in lipogenic tissues is similar antigenically to the enzyme in gluconeogenic tissues and that the soluble activities of pyruvate carboxylase detected in many rat tissues do not represent discrete enzymes but are the result of mitochondrial damage during tissue homogenization.

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