caa a22 4500 475745264 CHVBK 20180406123511.0 cr unu---uuuuu 170329e20001101xx s 000 0 eng 10.1023/A:1010344008224 doi (NATIONALLICENCE)springer-10.1023/A:1010344008224 Hydrogen peroxide Modulates Ca2+-Activation of Single permeabilized Fibres from Fast- and Slow-twitch Skeletal Muscles of Rats [Elektronische Daten] [David Plant, Gordon Lynch, David Williams] We examined the effects of redox modulation on single membrane-permeabilized fibre segments from the fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus muscles of adult rats to determine whether the contractile apparatus was the redox target responsible for the increased contractility of muscles exposed to low concentrations of H2O2. The effects of H2O2 on maximum Ca2+-activated force were dose-dependent with 30 min exposure to 5 mM H2O2 causing a progressive decrease by 22 ± 3 and 13 ± 2% in soleus and EDL permeabilized muscle fibres, respectively. Lower concentrations of exogenous H2O2 (100 μM and 1 mM) had no effect on maximum Ca2+-activated force. Subsequent exposure to the reductant dithiothreitol (DTT, 10 mM, 10 min) fully reversed the H2O2-induced depression of force in EDL, but not in soleus muscle fibres. Incubation with DTT alone for 10 min did not alter Ca2+-activated force in either soleus or EDL muscle fibres. The sensitivity of the contractile filaments to Ca2+ (pCa50) was not altered by exposure to any concentration of exogenous H2O2. However, all concentrations of H2O2 diminished the Hill coefficient in permeabilized fibres from the EDL muscle, indicating that the cooperativity of Ca2+ binding to troponin is altered. H2O2 (5 mM) did not affect rigor force, which indicates that the number of crossbridges participating in contraction was not reduced. In conclusion, H2O2 may reduce the maximum Ca2+ activated force production in skinned muscle fibres by decreasing the force per crossbridge. Kluwer Academic Publishers, 2000 Plant David Department of Physiology, The University of Melbourne, 3010, Victoria, Australia aut Lynch Gordon Department of Physiology, The University of Melbourne, 3010, Victoria, Australia aut Williams David Department of Physiology, The University of Melbourne, 3010, Victoria, Australia aut Journal of Muscle Research & Cell Motility Kluwer Academic Publishers 21/8(2000-11-01), 747-752 0142-4319 21:8<747 2000 21 10974 https://doi.org/10.1023/A:1010344008224 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1010344008224 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Plant David Department of Physiology, The University of Melbourne, 3010, Victoria, Australia aut NATIONALLICENCE 700 1- Lynch Gordon Department of Physiology, The University of Melbourne, 3010, Victoria, Australia aut NATIONALLICENCE 700 1- Williams David Department of Physiology, The University of Melbourne, 3010, Victoria, Australia aut NATIONALLICENCE 773 0- Journal of Muscle Research & Cell Motility Kluwer Academic Publishers 21/8(2000-11-01), 747-752 0142-4319 21:8<747 2000 21 10974 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer