Recovery of slow skeletal muscle after injury in the senescent rat.
We studied the contractile, histological and biochemical characteristics of regenerating slow (soleus) muscles of aged rats and the effect of IGF-1 treatment on these parameters. Regenerating soleus muscles were studied 21 days after myotoxic injury. In senescent rats (24 month old), the in situ isometric maximal tetanic force (P0), resistance to fatigue (T20%P0) and shortening speed with an afterload of 20%P0 (SS20%P0) were lower (p<0.05) in regenerating soleus muscles as compared to uninjured controlateral soleus muscles. Moreover, the expression of type 1 myosin heavy chain (MHC-1) was decreased by injury in the soleus muscles of senescent rats (p<0.05). Furthermore, a single injection of IGF-1 (3 microg) into the soleus of senescent rats only slightly increased the level of sarcoplasmic reticulum type 2 Ca(2+)-ATPase in regenerating soleus muscles (p<0.01). Contrary to senescent animals, regenerating soleus of adult rats (10 month old) did not present significantly lower P0 and MHC-1 expression than uninjured controlateral muscles (p>0.05). In conclusion, the regeneration of a slow muscle is more uncompleted 3 weeks after myotoxic injury in senescent rats than in adult rats. It cannot be made more effective by a single injection of IGF-1 into the senescent slow muscle.
Laboratoire d'Etude de la Croissance Cellulaire, Régénération et Réparation Tissulaires, CNRS FRE 2412, Faculté des Sciences, Université Paris XII, Créteil, France.
Alban
A
Vignaud
Philippe
P
Noirez
Sophie
S
Besse
Michel
M
Rieu
Denis
D
Barritault
Arnaud
A
Ferry
D000375:Aging / Q000502:physiology*; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D006133:Growth Substances / Q000494:pharmacology*; D015151:Immunoblotting / Q000379:methods; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018763:Muscle Fatigue / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000293:injuries / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
D006133:Growth Substances; D007334:Insulin-Like Growth Factor I; D018995:Myosin Heavy Chains; D000252:Calcium-Transporting ATPases