Alterations of High-Energy Phosphate Compounds in the Skeletal Muscles of Rats Intoxicated with Diisopropylphosphorofluoridate (DFP) and Soman

Measurements of the time course of high energy phosphate splitting and energy liberation were performed on rapidly shortening Rana pipiens skeletal muscles. In muscles contracting 30 times against small loads (less the 0.02P), the ratio of explained heat + work (H + W) (calculated from the measured high energy phosphate splitting) to observed H + W (from myothermal and mechanical measurements) was 0.68 +/- 0.08 and is in agreement with results obtained in isometric tetani of R. pipiens skeletal muscle. In lightly afterloaded muscles which were tetanized for 0.6a and whose metabolism was arrested at 3.0 s after the beginning of stimulation, a similar ratio of explained H + W to observed H + W was obtained. However, in identical contractions in which metabolism was arrested at 0.5-0.75 s after the beginning of stimulation, the ratio of explained H + W to observed H + W declined significantly to values ranging from 0.15 to 0.40. These results suggest that rapid shortening at the beginning of contraction induces a delay between energy production and measurable high energy phosphate splitting. This interpretation was tested and confirmed in experiments in which one muscle of a pair contracted isometrically while the other contracted against a small afterload. The afterload and stimulus pattern were arranged so that at the time metabolism was arrested, 0.5 s after the beginning of stimulation, the total energy production by both muscles was the same. Chemical analysis revealed that the isotonically contracting muscle spilt only 25% as much high energy phosphate as did the isometrically contracting muscle.

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Depletion of high energy phosphate compounds in the tumor-bearing state and reversal after tumor resection

Surgery ◽

10.1016/s0039-6060(96)80074-2 ◽

1996 ◽

Vol 120 (3) ◽

pp. 534-541 ◽

Cited By ~ 9

Author(s):

Steven N. Hochwald ◽

Lawrence E. Harrison ◽

Jeffrey L. Port ◽

David Blumberg ◽

Murray F. Brennan ◽

...

Keyword(s):

Tumor Resection ◽

High Energy ◽

High Energy Phosphate ◽

Tumor Bearing ◽

Phosphate Compounds

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Energy balance studies in frog skeletal muscles shortening at one-half maximal velocity.

The Journal of General Physiology ◽

10.1085/jgp.84.3.347 ◽

1984 ◽

Vol 84 (3) ◽

pp. 347-359 ◽

Cited By ~ 12

Author(s):

E Homsher ◽

T Yamada ◽

A Wallner ◽

J Tsai

Keyword(s):

Skeletal Muscles ◽

Maximum Velocity ◽

High Energy ◽

Sartorius Muscle ◽

Maximal Velocity ◽

High Energy Phosphate ◽

The Mean ◽

S Period ◽

High Energy Phosphate Metabolism ◽

Frog Sartorius

High-energy phosphate metabolism and energy liberated as heat and work were measured in 3-s tetani of frog sartorius muscle at 0 degree C. Two contraction periods were studied: (a) a 0.35-s period of shortening near half-maximum velocity beginning after 2 s of isometric stimulation, and (b) a 0.65-s isometric period immediately following the shortening. There were no significant changes in levels of ATP, ADP, or AMP in the two contraction periods. The observed changes in inorganic phosphate and creatine levels indicated that the only significant reaction occurring was phosphocreatine splitting. The mean rate of high-energy phosphate splitting during the shortening, 1.60 +/- 0.23 mumol X g-1 X s-1 (n = 24), was about fivefold higher than that in the 1-s period in the isometric tetanus, 0.32 +/- 0.11 mumol X g-1 X s-1 (n = 17), observed in our previous study. The mean rate in the post-shortening period, 0.46 +/- 0.13 mumol X g-1 X s-1 (n = 17), was not significantly different from that in the 1-s period in the isometric tetanus. A large amount of heat plus work was produced during the shortening period, and this could be accounted for by simultaneous chemical changes. In the post-shortening period, the observed enthalpy was also accounted for by simultaneous chemical reactions. Thus, the present result is in sharp contrast to that obtained from a similar study performed at a shortening at Vmax, where an enthalpy excess was produced during shortening and an enthalpy deficit was produced during the period following the shortening.

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