Static stretch increases c-Jun NH2-terminal kinase activity and p38 phosphorylation in rat skeletal muscle.
Physical exercise and contraction increase c-Jun NH2-terminal kinase (JNK) activity in rat and human skeletal muscle, and eccentric contractions activate JNK to a greater extent than concentric contractions in human skeletal muscle. Because eccentric contractions include a lengthening or stretch component, we compared the effects of isometric contraction and static stretch on JNK and p38, the stress-activated protein kinases. Soleus and extensor digitorum longus (EDL) muscles dissected from 50- to 90-g male Sprague-Dawley rats were subjected to 10 min of electrical stimulation that produced contractions and/or to 10 min of stretch (0.24 N tension, 20-25% increase in length) in vitro. In the soleus muscle, contraction resulted in a small, but significant, increase in JNK activity (1.8-fold above basal) and p38 phosphorylation (4-fold). Static stretch had a much more profound effect on the stress-activated protein kinases, increasing JNK activity 19-fold and p38 phosphorylation 21-fold. Increases in JNK activation and p38 phosphorylation in response to static stretch were fiber-type dependent, with greater increases occurring in the soleus than in the EDL. Immunohistochemistry performed with a phosphospecific antibody revealed that activation of JNK occurred within the muscle fibers. These studies suggest that the stretch component of a muscle contraction may be a major contributor to the increases in JNK activity and p38 phosphorylation observed after exercise in vivo.
Boppart
M D
MD
Research Division, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02215, USA.
Hirshman
M F
MF
Sakamoto
K
K
Fielding
R A
RA
Goodyear
L J
LJ
D000818:Animals; D004789:Enzyme Activation; D048031:JNK Mitogen-Activated Protein Kinases; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012026:Reflex, Stretch / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases
D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases