Contraction and cation contents of skeletal soleus and EDL muscles in age-matched control and diabetic rats

Skeletal muscle atrophy and neuropathy are two of the major long-term complications of diabetes mellitus (DM). This article investigates the effect of streptozotocin (STZ)-induced type 1 DM on contraction and cation contents in soleus and EDL muscles compared to age-matched control rats. Adult Wistar rats were humanely killed and the soleus and EDL muscles located and excised rapidly and placed in organ baths. The muscles were electrically stimulated (EFS, 50 V, 1 ms, 1-50 Hz) and isometric contraction monitored using a chart recorder. At the end of the experiments the muscles were blotted, weighed, and dissolved in concentrated nitric acid for the measurements of cation contents. Diabetic rats have significantly (P < 0.05) reduced body and muscle weights and significantly (P < 0.05) elevated blood glucose (29.65 +/- 0.33 mM, n = 10) compared to control (6.06 +/- 0.21 mM, n = 10). EFS evoked frequency dependent contraction in both soleus and EDL muscles of healthy control rats. The response was significantly (P < 0.05, n = 8) increased in EDL compared to soleus. In the diabetic soleus and EDL muscles the force of contraction was significantly (P < 0.05, n = 8) reduced in both muscle types compared to control. The levels of total sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), zinc (Zn2+), copper (Cu2+), and iron (Fe2+) were significantly (P < 0.05) reduced in diabetic soleus and EDL muscles compared to control. The results indicate that STZ-induced skeletal muscle atrophy is associated with marked reductions in both the force of contraction and cation contents in EDL and soleus muscles of the rat.