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Hydrogen peroxide increases depolarization‐induced contraction of mechanically skinned slow twitch fibres from rat skeletal muscles
Author(s) -
Plant David R.,
Lynch Gordon S.,
Williams David A.
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2001.013369
Subject(s) - chemistry , contraction (grammar) , depolarization , dithiothreitol , caffeine , biophysics , endoplasmic reticulum , hydrogen peroxide , fast twitch muscle , skeletal muscle , anatomy , endocrinology , biochemistry , biology , enzyme
The effect of exogenous hydrogen peroxide (H 2 O 2 ) on excitation‐contraction (E‐C) coupling and sarcoplasmic reticulum (SR) function was compared in mechanically skinned slow twitch fibres (prepared from the soleus muscles) and fast twitch fibres (prepared from the extensor digitorum longus; EDL muscles) of adult rats. Equilibration (5 min) with 1 m m H 2 O 2 diminished the ability of the Ca 2+ ‐depleted SR to reload Ca 2+ in both slow ( P < 0.01) and fast twitch fibres ( P < 0.05) compared to control. Under conditions when all Ca 2+ uptake was prevented, 1 m m H 2 O 2 increased SR Ca 2+ ‘leak’ in fast twitch fibres by 24 ± 5 % ( P < 0.05), but leak was not altered in slow twitch fibres. Treatment with 1 m m H 2 O 2 also increased the peak force of low [caffeine] contracture by ∼45 % in both fibre types compared to control ( P < 0.01), which could be partly reversed following treatment with 10 m m dithiothreitol (DTT). The changes in SR function caused by 1 m m H 2 O 2 were associated with an ∼65 % increase in the peak height of depolarization‐induced contractile response (DICR) in slow twitch fibres, compared to control (no H 2 O 2 ; P < 0.05). In contrast, peak contractile force of fast twitch fibres was not altered by 1 m m H 2 O 2 treatment. Equilibration with 5 m m H 2 O 2 induced a spontaneous force response in both slow and fast twitch fibres, which could be partly reversed by 2 min treatment with 10 m m DTT. Peak DICR was also increased ∼40 % by 5 m m H 2 O 2 in slow twitch fibres compared to control (no H 2 O 2 ; P < 0.05). Our results indicate that exogenous H 2 O 2 increases depolarization‐induced contraction of mechanically skinned slow but not fast twitch fibres. The increase in depolarization‐induced contraction in slow twitch fibres might be mediated by an increased SR Ca 2+ release during contraction and/or an increase in Ca 2+ sensitivity.