Oxidation of pyruvate, malate, citrate, and cytosolic reducing equivalents by AS-30D hepatoma mitochondria

Dietzen, D.J.; Davis, E.J.

Archives of Biochemistry and Biophysics 305(1): 91-102

1993


ISSN/ISBN: 0003-9861
PMID: 8342959
DOI: 10.1006/abbi.1993.1397
Accession: 009146988

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Abstract
Mitochondria isolated from normal rat liver and AS-30D hepatoma were concurrently evaluated with regard to their bioenergetic and metabolic properties. AS-30D mitochondria oxidized many NAD-linked respiratory substrates at rates 1.5-4 times faster than those from liver, a fact which contributes to their diminished membrane depolarization on conversion from state 4 to state 3 respiration. AS-30D mitochondria exhibited no signs of a "truncated" Krebs cycle, nor did they oxidize malate preferentially based upon its origin in the cytosol or the mitochondrial matrix. In addition, beta-oxidation in AS-30D mitochondria was not sufficient to suppress respiratory CO2 production and induce pyruvate carboxylation to the extent observed in liver. Finally, AS-30D mitochondria were able to oxidize externally generated NADH in a reconstituted system, but in a manner independent of the transmembrane electrical potential (delta psi), suggesting that the malate-aspartate shuttle is not operable in vivo. This fact may necessitate the adaptations tumor cells make to reoxidize cytosolic NADH through glycolysis even in the presence of adequate oxygen.

Oxidation of pyruvate, malate, citrate, and cytosolic reducing equivalents by AS-30D hepatoma mitochondria