Hydrogen peroxide increases depolarization-induced contraction of mechanically skinned slow twitch fibres from rat skeletal muscles

Abstract

The effect of exogenous hydrogen peroxide (H2O2) 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 mM H2O2 diminished the ability of the Ca2+-depleted SR to reload Ca2+ in both slow (P < 0.01) and fast twitch fibres (P < 0.05) compared to control. Under conditions when all Ca2+ uptake was prevented, 1 mM H2O2 increased SR Ca2+ 'leak' in fast twitch fibres by 24 ± 5 % (P < 0.05), but leak was not altered in slow twitch fibres. Treatment with 1 mM H..