【摘要】The study aimed to investigate the changes induced by diabetes in diaphragm (DIA), extensor digitorumlongus (EDL), and soleus (SOL) contractility and histochemistry throughout a broad time span. The contractility and ATPase staining of DIA, EDL, and SOL from the streptozotocin-induced rats and age-matched control ratswere observed over a period ranging from 4 weeks to 16 weeks after streptozotocin treatment. Only the muscle weight-to-body weight ratio of EDL displayed a reduction. Twitch tension force and tetanic tension decreased, while the time to peak tension and half-relaxation time were prolonged in diabetic rats. The fatigue index of DIA demonstrated an increase from 4 weeks to 8 weeks and a decline from 12 weeks to 16 weeks after the induction of diabetes. Regarding fatigue indexes, EDL and SOL demonstrated an incremental trend during the time frame. For DIA and SOL in the diabetic rats, the proportion of type I fibers grew higher, while EDL revealed a similar composition as the control rats. Both the fiber areas of type I and type II fibers decreased in the diabetic rats. DIA, EDL, and SOL appeared to suffer from muscle atrophy. The contractile forces and speed-related properties were impaired in the diabetic rats. The increased fatigability was demonstrated in DIA at a later stage, whereas resistance to fatigue in DIA at an early stage of diabetes was noted. The endurance to fatigue decreased in EDL and SOL as well. The study indicated that the differential alterations of contractile properties were associated with streptozotocin-induced fiber transformation.
