A comparison of two anesthetic techniques for the study of rat skeletal muscle high-energy phosphates in vivo using 31P-NMR

The bioenergetic correlates of skeletal muscle fatigue were assessed in vivo with phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy. After surgical construction of latissimus dorsi muscle ventricles, seven beagles underwent 31P-NMR spectroscopy during 12-min exercise protocols at 25- and 85-Hz stimulation frequencies and during both isovolumetric and dynamic contractions. Exercise at 85 Hz was associated with significantly greater fatigue than exercise at 25 Hz. At both frequencies, the onset of exercise was associated with a marked increase in inorganic phosphate (Pi) and a decrease in phosphocreatine (PCr). As the muscle fatigued at 85 Hz but not at 25 Hz, the phosphorus spectra returned to near baseline with a decrease in Pi and increase in PCr. For a given amount of force generated, the Pi-to-PCr ratio was higher for dynamic contractions than for isovolumetric contractions. This study indicates that high-frequency fatigue is unlikely to result from the direct effects of high-energy phosphate metabolism and that contractions producing external work consume more metabolic energy than equally forceful isometric contractions.

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Efficiency of human skeletal muscle in vivo: comparison of isometric, concentric, and eccentric muscle action

Journal of Applied Physiology ◽

10.1152/jappl.1997.83.3.867 ◽

1997 ◽

Vol 83 (3) ◽

pp. 867-874 ◽

Cited By ~ 97

Author(s):

T. W. Ryschon ◽

M. D. Fowler ◽

R. E. Wysong ◽

A.-R. Anthony ◽

R. S. Balaban

Keyword(s):

Skeletal Muscle ◽

Steady State ◽

Production Rate ◽

Human Skeletal Muscle ◽

Atp Synthesis ◽

High Energy ◽

High Energy Phosphates ◽

Muscle Action ◽

Atp Production

Ryschon, T. W., Fowler, R. E. Wysong, A.-R. Anthony, and R. S. Balaban. Efficiency of human skeletal muscle in vivo: comparison of isometric, concentric, and eccentric muscle action. J. Appl. Physiol. 83(3): 867–874, 1997.—The purpose of this study was to estimate the efficiency of ATP utilization for concentric, eccentric, and isometric muscle action in the human tibialis anterior and extensor digitorum longus in vivo. A dynamometer was used to quantitate muscle work, or tension, while simultaneous 31P-nuclear magnetic resonance data were collected to monitor ATP, phosphocreatine, inorganic phosphate, and pH. The relative efficiency of the actions was estimated in two ways: steady-state effects on high-energy phosphates and a direct comparison of ATP synthesis rates with work. In the steady state, the cytosolic free energy dropped to the lowest value with concentric activity, followed by eccentric and isometric action for comparative muscle tensions. Estimates of ATP synthesis rates revealed a mechanochemical efficiency [i.e., ATP production rate/work (both in J/s)] of 15.0 ± 1.3% in concentric and 34.7 ± 6.1% in eccentric activity. The estimated maximum ATP production rate was highest in concentric action, suggesting an activation of energy metabolism under these conditions. By using direct measures of metabolic strain and ATP turnover, these data demonstrate a decreasing metabolic efficiency in human muscle action from isometric, to eccentric, to concentric action.

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Short-term reduction in dietary intake of magnesium causes deficits in brain intracellular free Mg2+ and [H+]i but not high-energy phosphates as observed by in vivo 31P-NMR

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research ◽

10.1016/s0167-4889(97)00077-3 ◽

1997 ◽

Vol 1358 (1) ◽

pp. 1-5 ◽

Cited By ~ 13

Author(s):

Burton M Altura ◽

Asefa Gebrewold ◽

Aimin Zhang ◽

Bella T Altura ◽

Raj K Gupta

Keyword(s):

Dietary Intake ◽

31P Nmr ◽

High Energy ◽

High Energy Phosphates ◽

Short Term

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31P-NMR study of resting in vitro rat diaphragm exposed to hypercapnia

Journal of Applied Physiology ◽

10.1152/jappl.1988.65.5.2270 ◽

1988 ◽

Vol 65 (5) ◽

pp. 2270-2277 ◽

Cited By ~ 12

Author(s):

R. S. Fitzgerald ◽

S. Howell ◽

W. E. Jacobus

Keyword(s):

31P Nmr ◽

Mechanical Performance ◽

High Energy ◽

31P Nmr Spectroscopy ◽

High Energy Phosphates ◽

Rat Diaphragm ◽

Nmr Study

We have reported previously that, when exposed to hypercapnia of various intensities, the diaphragm reduces its force of twitch and tetanic contractions in the in vitro rat preparation as well as in the in vivo dog preparation. The experiments reported here with 31P nuclear magnetic resonance (31P-NMR) spectroscopy attempt to examine cellular mechanisms that might be responsible for this deterioration in mechanical performance. Specifically they describe certain characteristics of this preparation and cautions needed to study the resting in vitro rat diaphragm with such techniques. Second, they report the response of intracellular pH (pHi), phosphocreatine (PCr), ATP, and inorganic phosphate (Pi) in the resting in vitro rat diaphragm exposed to long-term normocapnia or to long-term hypercapnia. The results show that 1) to maintain a viable preparation, it was necessary to keep the diaphragm extended to an area approximating that at functional residual capacity, 2) the diaphragm seemed quite capable of maintaining a constant pHi and constant contents of ATP and Pi during normocapnia, but there was a gradual decline in PCr, and 3) during hypercapnia there was a significant decrease in pHi, but the behavior of the phosphate metabolites was exactly as during normocapnia. The results suggest that the decrease in mechanical performance of the diaphragm is probably not due to a decrease in the availability of the high-energy phosphates, although they do not completely exclude this possibility or possibilities related to regional compartmentation.

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