ABSTRACT
The aim of this investigation was to study the effect of intramitochondrial acyl-CoA on the respiration of rabbit heart mitochondria over the whole range of stationary respiratory rates between States 4 and 3. The creatine phosphokinase system was used for stabilization of extramitochondrial adenine nucleotide concentration. It was shown that acyl-CoA depressed respiration more effectively in the intermediate range of respiration between States 4 and 3. The effect of acyl-CoA was negligible near State 4 and in State 3. These data are in line with our previous results concerning the dependence of the adenine nucleotide translocator control coefficient on the rate of mitochondrial respiration. Thus, our data suggest that long-chain acyl-CoA may regulate oxidative phosphorylation in heart mitochondria in vivo.
Subject(s)
Acyl Coenzyme A/metabolism , Mitochondria, Heart/enzymology , Animals , In Vitro Techniques , Mitochondria, Heart/metabolism , Mitochondrial ADP, ATP Translocases/metabolism , Oxidative Phosphorylation , Oxygen Consumption/drug effects , Palmitoylcarnitine/pharmacology , Rabbits , Rotenone/pharmacologyABSTRACT
The regulative role of adenine nucleotide translocators (ANTs) in oxidative phosphorylation has been estimated by the titration of respiration of isolated rabbit heart mitochondria with carboxyatractyloside in the presence of a non-rate limiting creatine phosphokinase ADP-regenerating system. It has been established that the respiration rate is not controlled by ANTs in the two extreme states, state 3 and state 4. On the other hand, at an intermediate respiration rate (30-70% of the state 3 respiration, which roughly corresponds to that under physiological conditions) the ANT control coefficient had a value of 0.62-0.75. Thus, ANTs seem to play a key role in the regulation of oxidative phosphorylation.
Subject(s)
Mitochondria, Heart/physiology , Mitochondrial ADP, ATP Translocases/physiology , Nucleotidyltransferases/physiology , Oxidative Phosphorylation , Animals , Atractyloside/analogs & derivatives , Oxygen Consumption , Phosphocreatine/metabolism , RabbitsABSTRACT
The rate and efficiency of energy transport were examined in a system containing isolated rabbit heart mitochondria, hexokinase, adenylate kinase and low concentrations of adenine nucleotides. Oxygen consumption by mitochondria and glucose-6-phosphate synthesis by hexokinase were registered. It was found that when adenylate kinase is active both in mitochondria and in the environmental solution, the rate and efficiency (glucose-6-phosphate/O ratio) of glucose-6-phosphate formation considerably increase. The effects of adenylate kinase activity are fully abolished by diadenosine pentaphosphate, an inhibitor of adenylate kinase.
Subject(s)
Adenylate Kinase/metabolism , Dinucleoside Phosphates , Hexokinase/metabolism , Mitochondria, Heart/metabolism , Phosphotransferases/metabolism , Adenine Nucleotides/pharmacology , Adenosine Diphosphate/metabolism , Adenosine Triphosphate/metabolism , Animals , Cytoplasm/enzymology , Energy Transfer , Kinetics , Models, Biological , Myocardium/enzymology , Oxygen Consumption , RabbitsABSTRACT
The effects of temporary coronary artery occlusion (TCAO) in vivo and ischemia in situ (autolysis) on mitochondrial functions and inner membrane permeability were investigated. It was found that one day after TCAO the permeability of inner membrane to H+ was increased 64% and the maximal activity of the glutamate plus malate oxidase system was reduced 35% with respect to control. The proton-electrochemical gradient and the rate of oxidative phosphorylation were decreased 35% and 55%, respectively. The most significant alterations during autolysis were observed in respiratory control ratio, state IV respiration and in H+ permeability of inner membrane. The H+ permeability of inner membrane increased progressively with time, and after 4 hr of autolysis it was 378% higher than the control. The data suggest that the alterations in energy transduction efficiency of mitochondria isolated from ischemic myocardium depend largely on the increase of inner membrane permeability to H+.
