Changes in signalling molecule levels in 10-day hindlimb immobilized rat muscles.
OBJECTIVE
Hindlimb immobilization produces similar percentage decreases in muscle mass in the predominantly type I soleus and type II vastus lateralis muscles. Consequently we hypothesized that the percentage changes in potential regulatory molecules for atrophy would be similar in the two muscle fibre types.


METHODS
Therefore, the purpose of the current study was to measure phosphorylated p38 MAPK and JNK, as well as the protein levels of p53, growth arrest and DNA damage-inducible 45 (GADD45), and full-length poly(ADP-ribose) polymerase (PARP) to determine whether their changes in expression in the soleus and vastus lateralis muscles were similar at 10th day of hindlimb immobilization in young rats.


RESULTS
Unexpectedly, preferential increases in phosphorylation of p38 MAPK and JNK and in the protein levels of p53, GADD45, as well as decreases in full-length PARP occurred in the soleus muscle, while only p38 phosphorylation increased in the white portion of the vastus lateralis muscle at 10th day of hindlimb immobilization.


CONCLUSIONS
Taken together, these results are interpreted to suggest that some of regulatory processes or kinetics in the atrophy of type I and II muscle fibres during limb immobilization may differ at the 10th day of limb immobilization.
Machida
S
S
Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, MO 65211, USA.
Booth
F W
FW
D000818:Animals; D004249:DNA Damage; D006614:Hindlimb; D007103:Immobilization; D047908:Intracellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases / Q000032:analysis; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000032:analysis*; D009124:Muscle Proteins / Q000032:analysis*; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000201:enzymology / Q000254:growth & development; D009133:Muscular Atrophy / Q000378:metabolism; D010766:Phosphorylation; D011065:Poly(ADP-ribose) Polymerases / Q000032:analysis; D011506:Proteins / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344; D016159:Tumor Suppressor Protein p53 / Q000032:analysis; D048051:p38 Mitogen-Activated Protein Kinases / Q000032:analysis; D000097642:GADD45 Proteins
D047908:Intracellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D009124:Muscle Proteins; D011065:Poly(ADP-ribose) Polymerases; D011506:Proteins; D016159:Tumor Suppressor Protein p53; D048051:p38 Mitogen-Activated Protein Kinases; D000097642:GADD45 Proteins