| Autor: |
Ruiter, Cornelis J. De, Wevers, Ron A., Engelen, Baziel G.M. Van, Verdijk, Peter W.L., Haan, Arnold De |
| Zdroj: |
Muscle & Nerve; June 1999, Vol. 22 Issue: 6 p704-711, 8p |
| Abstrakt: |
Adductor pollicis muscle function of a 21-year-old man with genetically confirmed Brody's disease (sarcoplasmic reticulum [SR] -Ca2+ATPase deficiency) was investigated to study the possible effects of reduced SR-Ca2+ATPase activity on muscle relaxation and force production. Following maximal electrical activation of the ulnar nerve, tetanic muscle half-relaxation time was greater in the patient (246 ± 10 ms) than control subjects (97 ± 4 ms, n = 8). During repetitive activation, there was a similar decline in maximal shortening velocity in the patient and controls, indicating a comparable reduction in cross-bridge cycling rate. The finding that the slowing of relaxation was greater in the patient (329 ms versus 138 ± 20 ms) suggests that there was a further reduction of SR-Ca2+ATPase activity in the patient's muscle during fatigue. Following a voluntary contraction, involuntary activity of the antagonist muscles facilitated force decline and masked the impaired relaxation in the patient. This antagonist-induced relaxation indicates that it might be difficult to establish impaired muscle relaxation with voluntary contractions. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 704711, 1999. |
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