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Titolo:
SLOWED RELAXATION IN FATIGUED SKELETAL-MUSCLE FIBERS OF XENOPUS AND MOUSE CONTRIBUTION OF [CA2-BRIDGES(](I) AND CROSS)
Autore:
WESTERBLAD H; LANNERGREN J; ALLEN DG;
Indirizzi:
KAROLINSKA INST,DEPT PHYSIOL & PHARMACOL S-17177 STOCKHOLM SWEDEN
Titolo Testata:
The Journal of general physiology
fascicolo: 3, volume: 109, anno: 1997,
pagine: 385 - 399
SICI:
0022-1295(1997)109:3<385:SRIFSF>2.0.ZU;2-P
Fonte:
ISI
Lingua:
ENG
Soggetto:
SARCOPLASMIC-RETICULUM; INTRACELLULAR-PH; SINGLE FIBERS; RABBIT SKELETAL; CELLULAR MECHANISMS; TETANIC STIMULATION; ISOMETRIC TENSION; FORCE GENERATION; CALCIUM; PHOSPHATE;
Keywords:
[CA2+](I)-FORCE RELATION; SARCOPLASMIC RETICULUM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
57
Recensione:
Indirizzi per estratti:
Citazione:
H. Westerblad et al., "SLOWED RELAXATION IN FATIGUED SKELETAL-MUSCLE FIBERS OF XENOPUS AND MOUSE CONTRIBUTION OF [CA2-BRIDGES(](I) AND CROSS)", The Journal of general physiology, 109(3), 1997, pp. 385-399

Abstract

Slowing of relaxation is an important characteristic of skeletal muscle fatigue. The aim of the present study was to quantify the relative contribution of altered Ca2+ handling (calcium component) and factors downstream to Ca2+ (cross-bridge component) to the slowing of relaxation in fatigued fibers of Xenopus and mouse. Two types of Xenopus fibers were used: easily fatigued, type 1 fibers and fatigue resistant, type 2 fibers. In these Xenopus fibers the free myoplasmic [Ca2+] ([Ca2+](i)) was measured with indo-1, and the relaxation of Ca2+-derived force, constructed from tetanic [Ca2+](i) records and in vivo [Ca2+](i)-force curves, tvas analyzed. An alternative method was used in both Xenopus and mouse fibers: fibers were rapidly shortened during the initialphase of relaxation, and the time to the peak of force redevelopment nas measured. These two methods gave similar results and showed proportional slowing of the calcium and cross-bridge components of relaxation in both fatigued type 1 and type 2 Xenopus fibers, whereas only the cross-bridge component was slowed in fatigued mouse fibers. Ca2+ removal from the myoplasm during relaxation was markedly less effective in Xenopus fibers as compared to mouse fibers. Fatigued Xenopus fibers displayed a reduced rate of sarcoplasmic reticulum Ca2+ uptake and increased sarcoplasmic reticulum Ca2+ leak. Some fibers were stretched at various times during relaxation. The resistance to these stretches was increased during fatigue, especially in Xenopus fibers, which indicates that longitudinal movements during relaxation had become less pronounced and this might contribute to the increased cross-bridge componentof relaxation in fatigue. In conclusion, slowing of relaxation in fatigued Xenopus fibers is caused by impaired Ca2+ handling and altered cross-bridge kinetics, whereas the slowing in mouse fibers is only due to altered cross-bridge kinetics.

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Documento generato il 03/04/20 alle ore 08:01:09