Figure 2.

Sunitinib improves specific muscle contractile function and overall muscle strength. Muscle isometric contractility and strength assessments performed on 12-week-old mdx mice. (A) Single 1 Hz pulses generated isometric twitch force outputs showing the severe decline in diaphragm muscle twitch between WT (N = 5) and mdx vehicle-treated muscle (N = 11); Sunitinib-treated muscle (N = 11) twitch is significantly increased compared to vehicle treated. (B) Isometric tetanic stimuli performed at 100 Hz on diaphragm muscle showing a significant decline in tetanic force output between WT (N = 5) and vehicle-treated muscle (N = 11), Sunitinib treatment (N = 11) increased isometric tetanic force compared to vehicle treatment. (C) Isometric force performed at increasing stimulation frequencies; Sunitinib treatment increased force production in the 50–150 Hz frequency stimulations when compared to vehicle-treated muscle. (D) Muscle exhaustion depicted as decreased forelimb grip strength is apparent in vehicle-treated mdx mice compared to WT mice at trials 5 and 6. No significant change in forelimb force is observed between WT and Sunitinib-treated mdx mice during the six trials; Sunitinib-treated mdx mice are stronger than the vehicle treated in trials 4–6 suggesting less muscle exhaustion. Data assessed for significance using one-way ANOVA and statistical significance of mean ± SEM; WT versus mdx vehicle treatment #P < 0.05, ##P < 0.01, ###P < 0.001; WT versus mdx-Sunitinib treatment ++P < 0.01, +++P < 0.001; mdx vehicle treatment versus mdx-Sunitinib treatment ^*P < 0.05, ^**P < 0.01.