title: Glycogen phosphorylase and pyruvate dehydrogenase transformation in white muscle of trout during high-intensity exercise.
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 micromol x g wet tissue(-1) x 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 micromol x g wet tissue(-1) x 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.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada. richarjg@mcmaster.ca
authors.forename: Jeff G
authors.initials: JG
authors.lastname: Richards
authors.forename: George J F
authors.initials: GJ
authors.lastname: Heigenhauser
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
mesh_terms: D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D004734:Energy Metabolism; D024981:Glycogen Phosphorylase / Q000378:metabolism*; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D030481:Pyruvate Dehydrogenase (Lipoamide) / Q000378:metabolism*
chemical_list: D010725:Phosphocreatine; D000249:Adenosine Monophosphate; D000255:Adenosine Triphosphate; D030481:Pyruvate Dehydrogenase (Lipoamide); D024981:Glycogen Phosphorylase