COMPARISON OF CONTRACTILE PROPERTIES BETWEEN SLOW AND FAST SKELETAL MUSCLES OF FEMALE DIABETIC SPRAGUE-DAWLEY RATS

Contractile Properties of Slow and Fast Skeletal Muscles

Abstract

Objective: To compare isometric contraction, force-frequency relationship and muscle fatigue between slow and fast muscles of female type 2 diabetes mellitus Sprague-Dawley rats.
Study Design: Experimental study.
Place and Duration of Study: Physiology Department, Army Medical College, Rawalpindi and National Institute of Health, Islamabad from Jan to Dec 2015.
Material and Methods: Twenty healthy female Sprague Dawley rats were divided into 2 groups with 10 rats in each group. Group-I (control) was fed with normal diet and group-II (diabetic) was given high fat diet. Group-II was given intraperitoneal streptozotocin (STZ) (35mg/kg body weight) on 15th day. Body weight, blood glucose and TG: HDL ratio were estimated on 21st day to confirm type II diabetes mellitus (T2DM) induction. Soleus and extensor digitorum longus (EDL) muscles were removed intact and fixed in organ bath system containing Krebs Ringer buffer solution and connected to data acquisition unit (iWorx) to study their contractile parameters.
Results: Isometric twitch tensions of slow (soleus) and fast (EDL) muscles were similar in diabetic and control rats. Contraction and half relaxation times were slower in diabetic soleus muscles in comparison to control muscles. Diabetic soleus and EDL muscles displayed significantly (p<0.05) increased fatigability.
Conclusion: In STZ induced type II diabetic slow muscles, the tetanic tension remains unaffected while contraction and half relaxation times were longer. In fast muscles, tetanic tension and the speed related properties remain unaffected. There was reduction in resistance to and recovery from fatigue in both slow and fast skeletal muscles.