title: The influence of rat suspension-hypokinesia on the gastrocnemius muscle.
abstract: Hind-limb hypokinesia was induced in rats by the Morey method to characterize the response of the gastrocnemius muscle. A comparison of rats suspended for 2 weeks with weight, sex, and litter-matched control rats indicate no difference in gastrocnemius wet weight, contraction, or one-half relaxation times, but less contractile function as indicated by lowered dP/dt. Myosin ATPase staining identified uniform Type I (slow-twitch) and II (fast-twitch) atrophy in the muscles from 4 of 10 rats suspended for 2 weeks and 1 of 12 rats suspended for 4 weeks; muscles from three other rats of the 4-week group displayed greater Type I atrophy. Other histochemical changes were characteristic of a neuropathy. These data together with recently acquired soleus data (29) indicate the Morey model, like space flight, evokes greater changes in the Type I or slow twitch fibers of the gastrocnemius and soleus muscles.
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis; D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D006614:Hindlimb; D007103:Immobilization; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000473:pathology* / Q000503:physiopathology; D009133:Muscular Atrophy / Q000503:physiopathology*; D011187:Posture; D051381:Rats; D012149:Restraint, Physical; D013997:Time Factors
chemical_list: D000251:Adenosine Triphosphatases