AIMIn order to elucidate the underlying mechanism of depressed maximal isometric twitch tension normalized by cross sectional area of muscle strip in unloaded soleus.

METHODSThe soleus and extensor digitorum longus (EDL) muscle strips were perfused in vitro and treated by 2,3-Butanedione monoxime (BDM).

RESULTSThe BDM decreased Pt of soleus and EDL in a concentration-dependent manner. The Pt could restored completely to normal level after washing out BDM. The isometric twitch duration was not altered during 1 mmol/L BDM of perfusion, but was shortened at 10 mmol/L dose. The time from maximal to half Pt in EDL was shorter than that in soleus during 10 mmol/L BDM of perfusion. The inhibitory effects of BDM on myosin ATPase activity were higher in EDL than in soleus. The inhibitory extent of BDM on myosin ATPase activity of soleus and EDL was lower than that on Pt.

CONCLUSIONThese results suggest that reduction in cross-bridge function of skeletal muscle may be one of reasons induced a decrease in its Pt. BDM is not a specific inhibitor on myosin ATPase activity and can affect multiple parts of excitation-contraction coupling in skeletal muscle.