Glycogen phosphorylase and pyruvate dehydrogenase transformation in white muscle of trout during high-intensity exercise

Jeff G. Richards, George J.F. Heigenhauser, Chris M. Wood

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

We examined the regulation of glycogen phosphorylase (Phos) and pyruvate dehydrogenase (PDH) in white muscle of rainbow trout during a continuous bout of high-intensity exercise that led to exhaustion in 52 s. The first 10 s of exercise were supported by creatine phosphate hydrolysis and glycolytic flux from an elevated glycogenolytic flux and yielded a total ATP turnover of 3.7 μmol·g wet tissue-1·s-1. The high glycolytic flux was achieved by a large transformation of Phos into its active form. Exercise performed from 10 s to exhaustion was at a lower ATP turnover rate (0.5 to 1.2 μmol·g wet tissue-1·s-1) and therefore at a lower power output. The lower ATP turnover was supported primarily by glycolysis and was reduced because of posttransformational inhibition of Phos by glucose 6-phosphate accumulation. During exercise, there was a gradual activation of PDH, which was fully transformed into its active form by 30 s of exercise. Oxidative phosphorylation, from PDH activation, only contributed 2% to the total ATP turnover, and there was no significant activation of lipid oxidation. The time course of PDH activation was closely associated with an increase in estimated mitochondrial redox (NAD+-to-NADH concentration ratio), suggesting that O2 was not limiting during high-intensity exercise. Thus anaerobiosis may not be responsible for lactate production in trout white muscle during high-intensity exercise.

Original languageEnglish (US)
Pages (from-to)R828-R836
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume282
Issue number3 51-3
DOIs
StatePublished - 2002

Keywords

  • Adenosine 5′-triphosphate turnover
  • Cytoplasmic redox
  • Lactate
  • Mitochondrial redox
  • Oxygen limitation
  • Rainbow trout

ASJC Scopus subject areas

  • Physiology

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