Systemic lactate kinetics during graded exercise in man

Stanley, William C.; Gertz, Edward W.; Wisneski, Judith A.; Morris, D. Lynn; Neese, Richard A.; Brooks, George A.

doi:10.1152/ajpendo.1985.249.6.e595

Cited by 124 publications

(156 citation statements)

References 21 publications

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“…Also, greater stimulation of lactate fluxes may not be possible for trout because their baseline levels could already be quite high. This notion is supported by the fact that the R a /Ṁ O2 ratios of trout and humans are similar during intense exercise (8.9 for trout versus 6.4 for humans), but much higher in resting trout (19.5) than in resting humans (only 2.9) (Stanley et al, 1985; present study).…”

Section: The Journal Of Experimental Biology 216 (24)supporting

confidence: 78%

“…Moreover, humans can increase lactate production by 22-fold over resting values during a graded exercise protocol similar to what was used here for fish (Stanley et al, 1985). Trout may only be able to show a modest relative increase in flux because their metabolic scope is much smaller than that of mammals (Brett, 1972).…”

Section: The Journal Of Experimental Biology 216 (24)mentioning

confidence: 83%

“…Animals process lactate at high rates even under resting, normoxic conditions, and in mammals, many studies have shown that inherently high baseline lactate fluxes are strongly stimulated during exercise (Bergman et al, 1999;Donovan and Brooks, 1983;Issekutz et al, 1976;Stanley et al, 1985;Van Hall et al, 2003;Weber et al, 1987). Little is known about lactate fluxes in fish because adequate methods to quantify these fluxes accurately under controlled exercise conditions have only recently become available.…”

Section: Introductionmentioning

confidence: 99%

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Lactate kinetics of rainbow trout during graded exercise: Do catheters affect the cost of transport?

Teulier

Omlin

Weber

2013

Journal of Experimental Biology

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Section: The Journal Of Experimental Biology 216 (24)supporting

confidence: 78%

Section: The Journal Of Experimental Biology 216 (24)mentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

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Lactate kinetics of rainbow trout during graded exercise: Do catheters affect the cost of transport?

Teulier

Omlin

Weber

2013

Journal of Experimental Biology

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“…where E1 and E2 are the arterial whole blood isotope enrichments at sample times 1 (t1) and 2 (t2) (min), respectively; C1 and C2 are the arterial whole blood concentrations at t1 and t2 (mmol/l), respectively; and pV is the volume of distribution of 0.10 and 0.18 l/kg body wt for lactate and glucose, respectively (29). Although pV for both lactate and glucose has been used previously in studies of lactate and glucose kinetics, the assumption that this value is appropriate for resting and exercise conditions is obviated by the presence of a nearsteady-state condition.…”

Section: Methodsmentioning

confidence: 99%

Similar carbohydrate but enhanced lactate utilization during exercise after 9 wk of acclimatization to 5,620 m

Hall

Calbet

Söndergaard

et al. 2002

American Journal of Physiology-Endocrinology and Metabolism

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-We hypothesized that reliance on lactate as a means of energy distribution is higher after a prolonged period of acclimatization (9 wk) than it is at sea level due to a higher lactate R a and disposal from active skeletal muscle. To evaluate this hypothesis, six Danish lowlanders (25 Ϯ 2 yr) were studied at rest and during 20 min of bicycle exercise at 146 W at sea level (SL) and after 9 wk of acclimatization to 5,260 m (Alt). Whole body glucose R a was similar at SL and Alt at rest and during exercise. Lactate R a was also similar for the two conditions at rest; however, during exercise, lactate R a was substantially lower at SL (65 mol ⅐ min Ϫ1 ⅐ kg body wt Ϫ1 ) than it was at Alt (150 mol ⅐ min Ϫ1 ⅐ kg body wt Ϫ1 ) at the same exercise intensity. During exercise, net lactate release was ϳ6-fold at Alt compared with SL, and related to this, tracer-calculated leg lactate uptake and release were both 3-or 4-fold higher at Alt compared with SL. The contribution of the two legs to glucose disposal was similar at SL and Alt; however, the contribution of the two legs to lactate R a was significantly lower at rest and during exercise at SL (27 and 81%) than it was at Alt (45 and 123%).In conclusion, at rest and during exercise at the same absolute workload, CHO and blood glucose utilization were similar at SL and at Alt. Leg net lactate release was severalfold higher, and the contribution of leg lactate release to whole body lactate R a was higher at Alt compared with SL. During exercise, the relative contribution of lactate oxidation to whole body CHO oxidation was substantially higher at Alt compared with SL as a result of increased uptake and subsequent oxidation of lactate by the active skeletal muscles.glucose; isotopes; [1-13 C]lactate CARBOHYDRATE AND LACTATE METABOLISM is altered by hypoxia. Carbohydrate oxidation under hypoxic conditions has been suggested to be the preferable metabolic pathway during exercise, because it provides the highest ATP yield per mole of oxygen (3,15,16). Thus any increase in the percentage of energy derived from carbohydrate sources will result in a more economical use of oxygen. Indeed, results from studies in high-altitude natives (17) and lowlanders exposed to high altitude (5, 27) show a shift toward increased blood glucose utilization relative to normoxic conditions. However, McClelland et al. (23) reported that rats acclimatized to severe hypoxia did not increase carbohydrate utilization compared with normoxic conditions. Moreover, women acclimatized for 10 days to 4,300 m had a tendency for a lower contribution of carbohydrate oxidation to total energy expenditure during exercise, and they had a similar blood glucose disposal compared with sea level (2). In addition, Young et al. (35) suggested that, after chronic hypoxia exposure, increased mobilization and use of free fatty acids during exercise resulted in sparing of muscle glycogen. Thus there is no consensus in the literature with regard to metabolic fuel selection under hypoxic conditions. Some of the differences ob...

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“…Myocardial lactate uptake during exercise is increased as a function of the arterial lactate concentration (16,23,38), which is dependent on the rate of systemic lactate production and clearance (39). In addition, studies in resting dogs (37) and perfused rat hearts (15) demonstrate that an elevation in arterial lactate concentration reduces the relative contribution of fatty acids to MV O 2 (37).…”

mentioning

confidence: 99%

Regulation of myocardial substrate metabolism during increased energy expenditure: insights from computational studies

Zhou

Cabrera²,

Okere³

et al. 2006

American Journal of Physiology-Heart and Circulatory Physiology

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. Regulation of myocardial substrate metabolism during increased energy expenditure: insights from computational studies. Am J Physiol Heart Circ Physiol 291: H1036-H1046, 2006. First published April 21, 2006 doi:10.1152/ajpheart.01382.2005.-In response to exercise, the heart increases its metabolic rate severalfold while maintaining energy species (e.g., ATP, ADP, and Pi) concentrations constant; however, the mechanisms that regulate this response are unclear. Limited experimental studies show that the classic regulatory species NADH and NAD ϩ are also maintained nearly constant with increased cardiac power generation, but current measurements lump the cytosol and mitochondria and do not provide dynamic information during the early phase of the transition from low to high work states. In the present study, we modified our previously published computational model of cardiac metabolism by incorporating parallel activation of ATP hydrolysis, glycolysis, mitochondrial dehydrogenases, the electron transport chain, and oxidative phosphorylation, and simulated the metabolic responses of the heart to an abrupt increase in energy expenditure. Model simulations showed that myocardial oxygen consumption, pyruvate oxidation, fatty acids oxidation, and ATP generation were all increased with increased energy expenditure, whereas ATP and ADP remained constant. Both cytosolic and mitochondrial NADH/NAD ϩ increased during the first minutes (by 40% and 20%, respectively) and returned to the resting values by 10 -15 min. Furthermore, model simulations showed that an altered substrate selection, induced by either elevated arterial lactate or diabetic conditions, affected cytosolic NADH/NAD ϩ but had minimal effects on the mitochondrial NADH/NAD ϩ , myocardial oxygen consumption, or ATP production. In conclusion, these results support the concept of parallel activation of metabolic processes generating reducing equivalents during an abrupt increase in cardiac energy expenditure and suggest there is a transient increase in the mitochondrial NADH/NAD ϩ ratio that is independent of substrate supply.diabetes; exercise; heart; lactate; mitochondria; modeling CARDIAC PUMP FUNCTION is fueled by ATP hydrolysis, which is precisely matched by ATP formation, primarily in the mitochondria (42). In the transition from rest to intense exercise, there is a three-to sixfold increase in the rate of cardiac power generation, myocardial oxygen consumption (MV O 2 ), and ATP turnover (25). Nevertheless, at high work states the myocardial ATP and ADP concentrations are maintained at a relatively constant level (2, 4, 36). There is rapid activation of NADH generation in the mitochondria, flux through the electron transport chain (ETC), and ATP production by oxidative phosphorylation to match exactly ATP breakdown in the cytosol. Studies in isolated mitochondria show that the generation of NADH from carbon substrates, oxygen consumption, and oxidative phosphorylation are turned on by feedback from an increase in ADP concentration (9); however, the regul...

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Systemic lactate kinetics during graded exercise in man

Cited by 124 publications

References 21 publications

Lactate kinetics of rainbow trout during graded exercise: Do catheters affect the cost of transport?

Lactate kinetics of rainbow trout during graded exercise: Do catheters affect the cost of transport?

Similar carbohydrate but enhanced lactate utilization during exercise after 9 wk of acclimatization to 5,620 m

Regulation of myocardial substrate metabolism during increased energy expenditure: insights from computational studies

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