Fractions and Respiratory Decline

After the basic aspects of respiratory decline had been clarified in liver slices, attempts were made to study the phenomenon with liver mitochondria since they are the main site of respiratoiy activity in the cell. It was surprising to see that isolated mitochondria of prenecrotic livers, in contrast to intact liver slices, demonstrated a behavior which was in most respects indistinguishable from that of normal mitochondria which were obtained from vitamin E-supplemented animals (Corwin and Schwarz, 1959). The only consistent difference existed in the utilization of oxal-acetate. All other areas of substrate utilization in the citric acid cycle appeared normal. The impairment of oxalaeetate metabolism became evident when malate or succinate was used as substrate in the presence of DPN. In the sequence from succinate through malate to oxalaeetate, accumulation of oxalaeetate leads to an inhibition of oxygen consumption. 

Lack or Correlation between TBA-Reactive Material and Respiratory Decline (Addition op Fresh Homogenate to Declining System) 

Time (min) TBA reading O2 consumption M atoms [O] TBA reading O2 consumption M atoms 10] 

Since mitochondria behaved almost normally whereas whole liver slices of the same animals showed severe respiratory failure, it seemed logical to suspect as the cause of the respiratory breakdown an interaction between other cellular constituents and the respiring mitochondria. Isolated mitochondria or a combination of mitochondria and the supernatant fraction lose only about 25 % of their oxidative capacity over a 90-minute incubation time, but addition of the microsome fraction to either system produces 

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