Mitochondrial-Cytosolic Interactions in Perfused Rat Heart ROLE OF COUPLED TRANSAMINATION IN REPLETION OF CITRIC ACID CYCLE INTERMEDIATES

摘要: Abstract The kinetics of changes in the tissue content citric acid cycle intermediates and free amino acids have been investigated isolated perfused hearts during transition from substrate-free perfusion to with medium containing 5 mm glucose x 10-3 units insulin per ml. Glycolytic flux increased within 1 min about 300 µmoles equivalents g (dry weight) hour, oxygen uptake by 18 28% a basal rate 3000 µatoms hour. ratio lactate pyruvate fluid showed transient rise value 0.4 peak after 2 reached final steady state 4. contents oxalacetate aspartate decreased 76 59%, respectively, first 3 min, whereas glutamate reciprocally 230%. malate, citrate, alanine more gradually over 12-min period 4.3-, 8.6-, 4.4-fold, respectively. α-ketoglutarate initially rapidly then fell before rising again values 2-fold greater than initial. other glutamate, aspartate, were minor. Net accumulation heart following addition can be accounted for double transamination between aminotransferases. Creatine-P levels 14 weight), inorganic phosphate 12 weight). These together observed increase ATP:ADP 10.8 14.2 indicate higher energy adenine nucleotide system addition. From measured rates metabolism, uptake, contents, previously verified assumption that glycolytically generated NADH is transported mitochondria via malate-aspartate cycle, calculations made through steps anion exchange reactions across mitochondrial membrane. data rapid α-ketoglutarate-malate upon insulin, but 1- 2-min delay onset glutamate-aspartate aminotransferase. This intramitochondrial was attributed low affinity carrier extramitochondrial presence high concentrations. citrate synthase increased, dehydrogenase decreased. It postulated these are direct consequence regulation influx A uniform except malate achieved fall common values. Increased acetyl-CoA levels, inhibition enzyme an succinyl-CoA levels. reciprocal reversals 1.5 competition aminotransferase, generation which overcomes product increasing concentration.