caa a22 4500 475744888 CHVBK 20180406123510.0 cr unu---uuuuu 170329e20001001xx s 000 0 eng 10.1023/A:1005609405435 doi (NATIONALLICENCE)springer-10.1023/A:1005609405435 Frog skeletal muscle fibers recovering from fatigue have reduced charge movement [Elektronische Daten] [Joseph Bruton, Péter Szentesi, Jan Lännergren, Håkan Westerblad, László Kovács, László Csernoch] Following prolonged exercise, muscle force production is often impaired. One possible cause of this force deficit is impaired intracellular activation. We have used single skeletal muscle fibers from the lumbrical muscle of Xenopus laevis to study the effects of fatigue on excitation-contraction coupling. Fatigue was induced in 13 intact fibers. Five fibers recovered in normal Ringer only (fatigued-only fibers). The remaining eight fibers were subjected to a brief hypotonic treatment (F-H fibers) that is known to prolong the effects of fatigue. Intramembrane charge movement, changes in intracellular calcium concentration ([Ca2+]i) and force transients were measured in a single Vaseline gap chamber under voltage clamp. In F-H fibers, membrane capacitance was reduced. Confocal microscopy showed that this was not due to closure of the transverse tubules. The amount of normalized intramembrane charge was reduced from 21.0 ± 2.8 nC/μF (n = 10) in rested fibers to 12.2 ± 1.1 nC/μF in F-H fibers. However, the voltage dependence of intramembrane charge movement was unchanged. In F-H fibers, force production was virtually abolished. This was the consequence of the greatly reduced [Ca2+]i accompanying a depolarizing pulse. In recovering fatigued-only fibers, while the maximal available charge was not significantly smaller (18.3 ± 1.1 nC/μF), both calcium and force were reduced, albeit to a lesser extent than in F-H fibers. The data are consistent with a model where fatigue reduces the number of voltage sensors in the t-tubules and, in addition, alters the coupling between the remaining functional voltage sensors and the calcium channels of the sarcoplasmic reticulum. Kluwer Academic Publishers, 2000 Bruton Joseph Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg 4, S-171 77, Stockholm, Sweden aut Szentesi Péter Department of Physiology, Medical and Health Science Centre, University of Debrecen, Cell Physiology Research Group of the Hungarian Academy of Sciences, Hungary aut Lännergren Jan Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg 4, S-171 77, Stockholm, Sweden aut Westerblad Håkan Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg 4, S-171 77, Stockholm, Sweden aut Kovács László Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg 4, S-171 77, Stockholm, Sweden aut Csernoch László Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg 4, S-171 77, Stockholm, Sweden aut Journal of Muscle Research & Cell Motility Kluwer Academic Publishers 21/7(2000-10-01), 621-628 0142-4319 21:7<621 2000 21 10974 https://doi.org/10.1023/A:1005609405435 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1005609405435 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Bruton Joseph Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg 4, S-171 77, Stockholm, Sweden aut NATIONALLICENCE 700 1- Szentesi Péter Department of Physiology, Medical and Health Science Centre, University of Debrecen, Cell Physiology Research Group of the Hungarian Academy of Sciences, Hungary aut NATIONALLICENCE 700 1- Lännergren Jan Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg 4, S-171 77, Stockholm, Sweden aut NATIONALLICENCE 700 1- Westerblad Håkan Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg 4, S-171 77, Stockholm, Sweden aut NATIONALLICENCE 700 1- Kovács László Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg 4, S-171 77, Stockholm, Sweden aut NATIONALLICENCE 700 1- Csernoch László Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg 4, S-171 77, Stockholm, Sweden aut NATIONALLICENCE 773 0- Journal of Muscle Research & Cell Motility Kluwer Academic Publishers 21/7(2000-10-01), 621-628 0142-4319 21:7<621 2000 21 10974 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer