Operation Everest II: muscle energetics during maximal exhaustive exercise

Abstract

To investigate the metabolic basis for the reduction in peak blood lactate concentration that occurs with maximal exercise after acclimatization to altitude, eight male subjects [maximal O2 uptake of 51.2 +/- 3.0 (SE) ml.kg-1.min-1] were acclimated to progressive hypobaria over a 40-day period. Before decompression (SL-1), at 380 and 282 Torr, and on return to sea level (SL-2) the subjects performed progressive cycle exercise to exhaustion. Analysis of muscle samples obtained from the vastus lateralis before exercise and at exhaustion indicated a pronounced reduction (P less than 0.05) in muscle lactate concentration (mmol/kg dry wt) at 282 Torr (39.2 +/- 11) compared with SL-1 (113 +/- 9.7), 380 Torr (94.6 +/- 18), and SL-2 (92.7 +/- 22). For the other glycolytic intermediates studied (glucose 1-phosphate, glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-bisphosphate, and pyruvate) only the increase in glucose 1-phosphate, glucose 6-phosphate, and fructose 6-phosphate were blunted (P less than 0.05) at 282 Torr. The reduction in muscle glycogen concentration during exercise was similar (P less than 0.05) for all environmental conditions. Although exercise resulted in reductions (P less than 0.05) in ATP and creatine phosphate averaging 30 and 51%, respectively, the magnitude of the change was not dependent on the degree of hypobaria. Inosine monophosphate was elevated (P less than 0.05) approximately 11-fold with exercise at both SL-1 and SL-2. These findings support the hypothesis that the lower lactate concentration observed at 282 Torr after exhaustive exercise is due to a reduction in anaerobic glycolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP consumption by sarcoplasmic reticulum Ca2+ pumps accounts for 50% of resting metabolic rate in mouse fast and slow twitch skeletal muscle

“…High-energy phosphates and muscle metabolites. Muscle metabolites were extracted from freeze-dried tissue (25,26), and both adenosine triphosphate (ATP) and inosine monophosphate (IMP) were measured by using ion-pair reversed-phase high-performance liquid chromatography procedures originally developed by Ingebretson et al (32) and subsequently modified by Green et al (25). Measurements of PCr and Cr were accomplished using fluorometric procedures (37) with modifications (24).…”

Endothelium-dependent vasorelaxation to the AMPK activator AICAR is enhanced in aorta from hypertensive rats and is NO and EDCF dependent

“…Following incubation with or without AICAR (2 mM) for 30 min, rings were quickly removed from the apparatus, snap frozen in liquid nitrogen, and stored at Ϫ80°C. Samples were freeze-dried under vacuum, weighed, cut into small pieces, and extracted for analysis of ZMP [the intracellular metabolite of AICAR responsible for AMPK activation (10)] and adenine nucleotide content by high-performance liquid chromatography as previ-ously described (25,32). ZMP (Sigma) was included in the methodological calibration standards and was clearly resolved from other peaks in standards and samples.…”

Metabolic, enzymatic, and transporter responses in human muscle during three consecutive days of exercise and recovery

“…For measurement of glycogen, glycolytic intermediates, the high-energy phosphates [ATP and phosphocreatine (PCr)], and related metabolites [creatine (Cr), inorganic phosphate (P i)], the frozen tissue was initially freeze dried and the constituents extracted according to procedures previously published (27,32,32). The adenine nucleotides (ATP, ADP, AMP) and IMP concentrations were measured using ion pair-reversed phase HPLC procedures originally developed by Ingebretson et al (43) and subsequently modified by our group (27). The glycolytic intermediates and high-energy phosphates and related metabolites were measured fluorometrically (52).…”