The effects of pH on the kinetics of fatigue and recovery in frog sartorius muscle

1985 ◽  
Vol 63 (11) ◽  
pp. 1435-1443 ◽  
Author(s):  
J. M. Renaud ◽  
G. W. Mainwood
Keyword(s):  
Extracellular Ph ◽  
Sartorius Muscle ◽  
Frog Sartorius Muscle ◽  
Fatigue Development ◽  
Effects Of Ph ◽  
Force Recovery ◽  
Ph Dependent ◽  
Contraction Cycle ◽  
Kinetics Of ◽  
Frog Sartorius

The effects of pH on the kinetics of fatigue and recovery in frog sartorius muscle were studied to establish whether the pH to which muscles are exposed (extracellular pH) has an effect on both the rate of fatigue development and recovery from fatigue. When frog sartorius muscles were stimulated with short tetanic stimuli at rates varying from 0.2 to 2.0 trains/s, a time- and frequency-dependent decrease in force development was observed, but extracellular pH had comparatively little effect. The recovery of tetanic force was dependent on the extracellular pH. This effect was characterized by a rapid recovery in force at pH 8.0 and an inhibition of recovery at pH 6.4 even when force decreased by only 25% during stimulation. Even when muscles were fatigued at pH 8.0 the rate of force recovery was still very small at pH 6.4. A model is proposed in which a step of the contraction cycle changes from a normal to a fatigued state. The rate of this transition is a function of the stimulation frequency and not pH. The reverse transition, from a fatigued to normal state is pH dependent; i.e., it is inhibited by H+. Measurements of resting and action potentials show that extracellular pH influences these parameters in the fatigue state, but there is no evidence that these changes are directly responsible for the pH-dependent step in the reversal of fatigue.

Seasonal variation in muscle fatigue in the sartorius muscle of the frog Rana pipiens

1991 ◽  
Vol 69 (6) ◽  
pp. 1712-1715
Author(s):  
Jean Marc Renaud
Keyword(s):  
Seasonal Variation ◽  
Rana Pipiens ◽  
Recovery Period ◽  
Sartorius Muscle ◽  
Tetanic Force ◽  
Fatigue Development ◽  
Significant Seasonal Variation ◽  
Significant Difference ◽  
Force Recovery ◽  
Frog Sartorius

The goal of this study was to determine whether seasonal variation occurs in the rates of fatigue development and force recovery in the frog sartorius muscle. The data were gathered from different experiments performed during a 6-year period (1983–1989). All frog sartorius muscles were stimulated to fatigue with tetanic contractions at the rate of 1/s for 3 min. The decrease in tetanic force after 1.5 and 3 min of stimulation was relatively consistent throughout the year. The only significant difference occurred in the muscles tested in September and October, which were less fatigue resistant than those tested in December. Following fatigue, muscles were stimulated at the rate of one contraction every 100 s, so that the recovery of tetanic force could be followed. A large and significant seasonal variation was observed in the recovery period. Frog sartorius muscles tested between March and July recovered their tetanic force at a faster rate than those tested between August and October. It was shown that the highest capacity to recover force coincides with the time of the year when frogs are the most active.

Is the change in intracellular pH during fatigue large enough to be the main cause of fatigue?

1986 ◽  
Vol 64 (6) ◽  
pp. 764-767 ◽  
Author(s):  
J. M. Renaud ◽  
Y. Allard ◽  
G. W. Mainwood
Keyword(s):  
Intracellular Ph ◽  
Extracellular Ph ◽  
Sartorius Muscle ◽  
Bathing Solution ◽  
Tetanic Contraction ◽  
Tetanic Force ◽  
Fatigue Effect ◽  
Frog Sartorius Muscle ◽  
Stimulation Period ◽  
Frog Sartorius

The intracellular pH of frog sartorius muscles exposed to an extracellular pH 8.0 (25 mM HCO3−, 1% CO2) was 6.9–7.1. Following a fatiguing stimulation period (one tetanic contraction per second for 3 min), the intracellular pH was 6.5–6.7. When similar experiments were repeated with frog sartorius muscles exposed to pH 6.4 (2 mM HCO3−, 1% CO2), the intracellular pH was 6.8–6.9 at rest and 6.3–6.4 following fatigue. So, in both experiments the intracellular pH decreased by 0.4–0.5 pH unit during fatigue. When the CO2 concentration of the bathing solution was increased from 1 to 30%, the intracellular pH of resting muscles decreased from 7.0 to 6.2–6.3. Although the effect of CO2 on the intracellular pH was greater than the fatigue effect, the decrease in tetanic force with CO2 was less than 40%, while during fatigue the tetanic force decreased by at least 70%. Therefore in frog sartorius muscle the decrease in tetanic force during fatigue exceeds the decrease that is expected from just a change in intracellular pH.

scholarly journals Kinetics of oxygen consumption after a single isometric tetanus of frog sartorius muscle at 20 degrees C.

1978 ◽  
Vol 71 (5) ◽  
pp. 559-580 ◽  
Author(s):  
M Mahler
Keyword(s):  
Oxygen Consumption ◽  
Time Course ◽  
Atp Hydrolysis ◽  
Preceding Paper ◽  
Nonlinear Process ◽  
Forthcoming Paper ◽  
Sartorius Muscle ◽  
Frog Sartorius Muscle ◽  
Kinetics Of ◽  
Frog Sartorius

The time-course of the rate of oxygen consumption (QO2) has been measured in the excised frog sartorius muscle after single isometric tetani of 0.1-1.0 s at 20 degrees C. To measure deltaQO2(t), the change in QO2 from its basal level, a novel method was devised, based on the validity in this tissue of the one-dimensional diffusion equation for oxygen, established in the preceding paper. After a tetanus, deltaQO2 reached a peak within 45-90 s, then declined exponentially, and could be well fit by deltaQO2(t) = QO + Q1(epsilon -k1t - epsilon-k2t). tau2 (= 1/k2), which characterized the rise of deltaQO2, was a decreasing function of tetanus duration (range: from 1.1 +/- 0.28 min [nu = 5] for a 0.1-s tetanus, to 0.34 +/- 0.05 min [nu = 8] for a 1.0-sec tetanus). tau1 (= 1/k1), which characterized the decline of deltaQO2, was not dependent on tetanus duration, with mean 3.68 +/- -.24 min (nu = 46). A forthcoming paper in this series shows that these kinetics of deltaQO2 are the responses to impulse-like changes in the rate of ATP hydrolysis. The variation of tau2 with tetanus duration thus indicates the involvement of a nonlinear process in the coupling of O2 consumption to ATP hydrolysis. However, the monoexponential decline of deltaQO2(t), with time constant independent of tetanus duration, suggests that during this phase, the coupling is rate-limited by a single reaction with apparent first order kinetics.

Constancy of Axial Spacings in Frog Sartorius Muscle during Contraction

Nature ◽  
1965 ◽  
Vol 206 (4991) ◽  
pp. 1358-1358 ◽  
Author(s):  
H. E. HUXLEY ◽  
W. BROWN ◽  
K. C. HOLMES
Keyword(s):  
Sartorius Muscle ◽  
Frog Sartorius Muscle ◽  
Frog Sartorius
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