title: Influence of exercise intensity on ERK/MAP kinase signalling in human skeletal muscle.
abstract: The mitogen-activated protein (MAP) kinase pathways have been highlighted as a possible link between exercise and adaptive changes in skeletal muscle. In this study, the effect of exercise intensity on the activation of the ERK/MAP kinase pathway was investigated in human skeletal muscle. One-leg exercise at low (40% maximal oxygen consumption, VO2max for 30 min) and high (75% VO2max for 30 min) intensity resulted in 11.5+8. I-fold and 39.7+/-6.3-fold (mean +/-SEM) increases in ERK1/2 phosphorylation (P<0.001), respectively. The phosphorylation of MEK1/2, the upstream kinase of ERK1/2, increased with exercise intensity (P<0.05) to 2.5+/-0.9 and 4.8+/-1.1 times the basal level at the low and high intensity, respectively. The statistical analysis revealed a systematic difference between basal, low and high intensity exercise levels for both kinases. There was no change in the phosphorylation of either kinase in the non-exercised leg. The phosphorylation of the transcription factor cyclic AMP response element binding protein (CREB), a possible downstream target of the ERK/MAP kinase signalling pathway, was unaffected by exercise. The phosphorylation of ERK1/2 was significantly higher in purified freeze-dried compared to crude wet muscle after exercise, whereas the opposite pattern was observed for CREB. In conclusion, phosphorylation of ERK1/2 and MEK1/2 increases in an exercise intensity-dependent manner in human skeletal muscle and this seems to originate in the muscle fibres themselves.
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: U
authors.initials: U
authors.lastname: Widegren
authors.forename: C
authors.initials: C
authors.lastname: Wretman
authors.forename: A
authors.initials: A
authors.lastname: Lionikas
authors.forename: G
authors.initials: G
authors.lastname: Hedin
authors.forename: J
authors.initials: J
authors.lastname: Henriksson
mesh_terms: D000328:Adult; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D005612:Freeze Drying; D006801:Humans; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology*; D010101:Oxygen Consumption; D010766:Phosphorylation; D015398:Signal Transduction
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases