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1. Muscle fatigue following long-duration rhythmic activity is often characterized by reduced force following a single impulse and at low-frequencies of stimulation. 2. Although this response is generally attributed to an alteration in excitation-contraction coupling, the possibility that the responsiveness of myofibrillar proteins to a given Ca2+ signal is altered has never been ruled out. 3. In this study, rat plantaris muscles were subjected to an in situ regimen of contractions (100 Hz, lasting 100 msec, once every 750 msec, for 1 hr), and allowed to recover for 15 min. 4. Twitch, 100 Hz, and 200 Hz forces were reduced by 79%, 49% and 17% respectively, at this time. 5. In myofibrils isolated from these muscles, maximum activity of Ca2+ activated myofibrillar ATPase, Ca2+ sensitivity (pCa 50), and co-operatively (Hill n), were not different from non-fatigued muscles. 6. It appears, therefore, that the Ca2+ activation properties of myofibrillar ATPase do not contribute to this pattern of fatigue.
R A Turcotte, and
H Oueslati, and
P F Gardiner
March 2002,
General physiology and biophysics,
R A Turcotte, and
H Oueslati, and
P F Gardiner
May 1998,
Journal of muscle research and cell motility,
R A Turcotte, and
H Oueslati, and
P F Gardiner
July 1965,
Biochimica et biophysica acta,
R A Turcotte, and
H Oueslati, and
P F Gardiner
October 1981,
Molecular and cellular biochemistry,
R A Turcotte, and
H Oueslati, and
P F Gardiner
January 1982,
Advances in myocardiology,
R A Turcotte, and
H Oueslati, and
P F Gardiner
January 1979,
Enzyme,
R A Turcotte, and
H Oueslati, and
P F Gardiner
October 1990,
The Journal of membrane biology,
R A Turcotte, and
H Oueslati, and
P F Gardiner
January 1989,
Biochimica et biophysica acta,
R A Turcotte, and
H Oueslati, and
P F Gardiner
January 1985,
The International journal of biochemistry,
R A Turcotte, and
H Oueslati, and
P F Gardiner
April 1998,
Muscle & nerve,
