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.

Fast water currents reduce production performance of post-smolt Atlantic salmon Salmo salar

“…ATP content did not differ between velocities. Depletion of ATP is closely linked to fatigue (McFarlane & McDonald 2002, Richards et al 2002, which indicates that, irrespective of current velocity, the fish in the present study did not deplete their energy reserves, nor were they close to fatigue. In addition, lactate levels were not elevated in the fast velocity treatment, which may have been expected if there was anaerobic swimming activity.…”

Hypoxia stimulates lactate disposal in rainbow trout

“…4B) that act in tandem to maintain a low and steady lactate concentration in the circulation (<1mmoll -1 ; Fig.1B). Work by Richards et al has shown that the pyruvate dehydrogenase complex probably plays a key regulatory role in sustaining lactate production in normoxic fish (Richards et al, 2002). Rainbow trout support higher baseline turnover rates for lactate (~15molkg ) (Haman et al, 1997b;Shanghavi and Weber, 1999;Weber and Shanghavi, 2000), and the same pattern has been observed in humans (Stanley et al, 1985;Weber et al, 1990).…”

Rapid evolution of muscle fibre number in post-glacial populations of Arctic charrSalvelinus alpinus

“…The immediate energy supply for contraction in the fast muscle comes from the hydrolysis of phosphocreatine and is supplemented by anaerobic glycogenolysis during prolonged high-speed swimming, resulting in the accumulation of lactic acid (Hochachka, 1985;Richards et al, 2002). The rate of radial diffusion of a substance is proportional to the reciprocal of the square root of the relative molecular mass, and is much greater for relatively large molecules such as lactate than oxygen (Kinsey and Moerland, 2002).…”