Contribution of the G-3-P shuttle to submaximal respiration in mitochondria from type IIb skeletal muscle

M. R. Jackman, W. T. Willis

Research output: Contribution to journalArticle

Abstract

It has been hypothesized that cytosolic reducing equivalents may assist mitochondrial oxidative phosphorylation. In support, addition of 10mM glycerol-3-phosphate (G-3-P) to type IIb mitochondria (MITO) respiring in the presence of 1mM pyruvate + 1mM malate (P+M), resulted in a doubling of the maximal respiration rate while reducing the ADP/O ratio to 2.15. Thus, under maximal conditions, addition of G-3-P resulted in partial displacement of P+M oxidation, and accounted for roughly 70% of the total oxygen consumption. In this study we evaluated the contribution of the G-3-P shuttle during submaximal respiration. MITO were isolated from the gracilis (99% type IIb) muscle of rabbit (n=5). Respiration was measured polarographically in the presence of a total adenylate pool of 5mM and constant 5mM Pi. Substrate provided was P+M. with or w/o 10mM G-3-P. The [ADP], ATP/ADP, and deltaGATP of the respiration medium were clamped to various levels using creatine kinase + a 50mM total creatine pool. Under all substrate conditions, respiration was found to be linear with deltaGATP. In comparison, respiration was significantly greater in the presence of P+M+G-3-P. Slopes of the P+M and P+M+G-3-P vs. deltaGATP regression lines were similar, suggesting that over the submaximal range investigated, the contribution of G-3-P is constant and independent of [ADP], ATP/ADP and deltaGATP. Collectively, we have demonstrated that the potential contribution of extramitochondrial reducing equivalents to respiration within MITO from type IIb muscle is substantial. Moreover, under submaximal conditions this contribution appears constant and independent of the energetic demand.

Original languageEnglish (US)
JournalFASEB Journal
Volume12
Issue number5
StatePublished - Mar 20 1998

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Mitochondria
Pyruvic Acid
Adenosine Diphosphate
breathing
malates
Muscle
skeletal muscle
glycerol
Respiration
Skeletal Muscle
mitochondria
phosphates
Adenosine Triphosphate
Creatine
Muscle Mitochondrion
Substrates
muscles
Creatine Kinase
creatine
oxidative phosphorylation

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Cell Biology

Cite this

Contribution of the G-3-P shuttle to submaximal respiration in mitochondria from type IIb skeletal muscle. / Jackman, M. R.; Willis, W. T.

In: FASEB Journal, Vol. 12, No. 5, 20.03.1998.

Research output: Contribution to journalArticle

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