Synergistic ablation does not affect atrophy or altered myosin heavy chain expression in the non-weight bearing soleus muscle.

Abstract	The purpose of this study was to investigate whether the soleus muscle undergoes atrophy and alterations in myosin heavy chain (MHC) composition during non-weight bearing in the absence of synergists. Thirty-two female rats were randomly assigned to four groups: control (C), synergistic ablation (ABL) of the gastrocnemius and plantaris muscles to overload the soleus muscle, hindlimb suspension (HLS), or a combination of synergistic ablation and hindlimb suspension (HLS-ABL). After 28 days of hindlimb suspension, soleus atrophy was more pronounced in HLS (58%) than in HLS-ABL (43%) rats. Compared to C rats, non-weight bearing decreased mixed and myofibrillar protein contents and Type I MHC 49%, 45%, and 7%, respectively, in HLS animals. In addition, de novo expression of fast Type IIx and Type IIb MHC (5% and 2%, respectively) was observed in HLS animals. Similarly, when compared to C rats, mixed and myofibrillar protein contents and Type I MHC decreased 43%, 46%, and 4%, respectively, in HLS-ABL animals. Also, de novo expression of Type IIx (4%) and IIb (1%) MHC was observed. Collectively, these data indicate that the loss of muscle protein and Type I MHC, and the de novo expression of Type IIx and Type IIb MHC in the rat soleus occur independently of the presence of synergists during non-weight bearing. Furthermore, these results confirm the contention that soleus mass and MHC expression are highly sensitive to alterations in mechanical load.
Authors	J K Linderman, R J Talmadge, K L Gosselink, P N Tri, R R Roy, R E Grindeland
Journal	Life sciences (Life Sci) Vol. 59 Issue 10 Pg. 789-95 ( 1996) ISSN: 0024-3205 [Print] Netherlands
PMID	8761312 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)
Chemical References	Muscle Proteins Myosin Heavy Chains
Topics	Animals Atrophy Female Immobilization Muscle Proteins (biosynthesis) Muscle, Skeletal (metabolism, pathology, physiopathology) Myosin Heavy Chains (biosynthesis) Organ Size Rats Rats, Sprague-Dawley Weight-Bearing

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