Submaximal Level Single Twitch Kinetics Dependent on Disease State in Duchenne Muscular Dystrophy Mouse Model

In muscular dystrophy research, it is pertinent to analyze the force of the muscles affected by the disease to assess pathology and to assess potential effectiveness of interventions. Maximal tetanic contractions are the most commonly used protocol to assess muscle function. However, the vast majority of in vivo muscle function is at submaximal contraction. Moreover, although force of contraction is assessed, the kinetics of the contraction are rarely reported. To investigate the effect of muscular dystrophy on twitch contraction kinetics, isolated diaphragm and extensor digitorum longus (EDL) of 20‐week untreated “het” (dystrophin deficient and utrophin haploinsufficient) and wild‐type C57 mice were analyzed. In isolated diaphragm strips, Time‐to‐Peak (TTP) is slower in “het” mice (14.2 ± 0.3 ms) than in C57 (11.5 ± 0.3 ms) mice, while no significant difference was identified for Time for 50% Relaxation (RT50) of the twitch contraction. In isolated EDL muscles, TTP was also slower in “het” mice (24.0 ± 0.4 ms) compared to C57 mice (20.7 ± 0.3 ms). Unlike the diaphragm, it was found that RT50 of EDL muscles is also disease‐dependent. The RT50 of “het” mice (15.3 ± 0.6 ms) was significantly slower than the C57 model (11.8 ± 0.2 ms). These findings suggest that not only is the maximal force of the muscles important, but also the kinetics of the muscles are impacted by disease. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .