As illustrated in Fig. 5B, there are no detectable effects of Ni2+ on the high-frequency tetanic force in aged muscles.
We found that BTP-2 reduce the high frequency tetanic force produced by EDL and SOL muscles from young mice (Fig. 7A and 7B), further suggesting that a component of force generation in young, healthy skeletal muscles derives from functional SOCE.
However, when comparisons were made between the resting force at high [Ca2+]o and the peak tetanic force at low [Ca2+]o, they were comparable for similar [Ca2+]i.
In contrast, the mdx 4H soleus generated 55% greater tetanic force and 66% higher specific force, while force production in the diaphragm was unchanged (Table 3, Fig. 7E).
Similarly, the normalized, maximum isometric tetanic force (Po) was higher in dy W /Bcl/mag mice than in dy W /mag mice (Fig 6C and D).
Other workers have studied the effect of antioxidants on force generation by skeletal muscle and demonstrated a reduction in submaximal force generation of nonfatigued muscle at low frequencies of stimulation, but no similar effects on maximal tetanic force generation have been reported, except where very high (and potentially toxic) concentrations of antioxidants were used (8, 29, 42, 44).
The peak isometric tetanic force (P0) produced by the soleus muscle was significantly higher in the controls compared to the Mariusz mice (P<0.05) (Figure 5B,C).
For example a brief 0.6 s long high-frequency pulse train delivered every 100 min led to a sixfold increase in tetanic force of denervated muscles (Westgaard & Lømo, 1988).
To assess ex vivo muscle function, time to peak tension and specific tetanic force of the tibialis anterior muscle were considered: HFD mice showed a significantly higher time to peak tension) and lower specific tetanic force) in comparison to control animals.
The muscle force produced at 20 and 100Hz was expressed as increasing values in tetanic force.
