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 language | English (US) |
---|---|
Pages (from-to) | R828-R836 |
Journal | American Journal of Physiology - Regulatory Integrative and Comparative Physiology |
Volume | 282 |
Issue number | 3 51-3 |
DOIs | |
State | Published - 2002 |
Keywords
- Adenosine 5′-triphosphate turnover
- Cytoplasmic redox
- Lactate
- Mitochondrial redox
- Oxygen limitation
- Rainbow trout
ASJC Scopus subject areas
- Physiology