Effect of exercise on activation of the p38 mitogen-activated protein kinase pathway, c-Jun NH2 terminal kinase, and heat shock protein 27 in equine skeletal muscle.
OBJECTIVE
To investigate the effects of exercise on activation of mitogen-activated protein kinase (MAPK) signaling proteins in horses.


METHODS
6 young trained Standardbred geldings.


METHODS
Horses performed a 20-minute bout of exercise on a treadmill at 80% of maximal heart rate. Muscle biopsy specimens were obtained from the vastus lateralis and pectoralis descendens muscles before and after exercise. Amount of expression and intracellular location of phosphospecific MAPK pathway intermediates were determined by use of western blotting and immunofluorescence staining.


RESULTS
Exercise resulted in a significant increase in phosphorylation of p38 pathway intermediates, c-Jun NH2 terminal kinase (JNK), and heat shock protein 27 (HSP27) in the vastus lateralis muscle, whereas no significant changes were found in phosphorylation of extracellular regulated kinase. In the pectoralis descendens muscle, phosphorylation of p38 and HSP27 was significantly increased after exercise. Immunohistochemical analysis revealed fiber-type- specific locations of phosphorylated JNK in type 2a/b intermediate and 2b fibers and phosphorylated p38 in type 1 fibers. Phosphorylated HSP27 was strongly increased after exercise in type 1 and 2a fibers.


CONCLUSIONS
The p38 pathway and JNK are activated in the vastus lateralis muscle after a single 20-minute bout of submaximal exercise in trained horses. Phosphorylation of HSP27 as detected in the study reported here is most likely induced through the p38 signaling pathway.
van Ginneken
Mireille M E
MM
Department of Equine Sciences, Medicine Section, Faculty of Veterinary Medicine, Utrecht University, PO Box 80153, NL3508 TD Utrecht, The Netherlands.
de Graaf-Roelfsema
Ellen
E
Keizer
Hans A
HA
van Dam
Klien G
KG
Wijnberg
Inge D
ID
van der Kolk
Johannes H
JH
van Breda
Eric
E
D000818:Animals; D004789:Enzyme Activation; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006736:Horses / Q000378:metabolism* / Q000502:physiology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008297:Male; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation; D010805:Physical Conditioning, Animal / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D006360:Heat-Shock Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases