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Peak force controls intracellular signaling after high force contractions, independent of metabolic stress
Author(s) -
Rahnert Jill A,
Burkholder Thomas J
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.801.12
Subject(s) - phosphorylation , isometric exercise , chemistry , signal transduction , p38 mitogen activated protein kinases , protein kinase b , duty cycle , microbiology and biotechnology , kinase , intracellular , endocrinology , medicine , protein kinase a , biology , biochemistry , power (physics) , physics , quantum mechanics
The increase in protein synthesis following resistance exercise has been attributed to the high forces generated, and activation of several signaling cascades appears to be force dependent. Both mechanical and metabolic stresses are present, and ATP depletion is aggravated by high duty cycle (HDC) protocols (i.e. 30% work:rest). We hypothesized that contraction‐induced signaling may reflect mechanical stress more than metabolic stress. Mechanical stress induced signaling was discriminated from metabolic stress by using low duty cycle (LDC, 2%) and HDC (30%) protocols. Mouse tibialis anterior muscles were subjected to 60 maximal isometric activations over 20 minutes and analyzed by Western blot. Peak forces were similar (1.31 N ± 0.25, HDC and 1.22N ± 0.22, LDC). Force decline was greater in the HDC (29%) than LDC (3%). Phosphorylation of ACC, indicative of AMP‐activated protein kinase (AMPK) activity, was markedly increased in the HDC protocol. Force generation of any duration reduced phosphorylation of Akt, increased ERK1/2, and had no effect on p70 s6k or 4EBP1. Phosphorylation of p38 was greater in the LDC than HDC protocol. We conclude that the immediate response to high force contractions is largely dependent on mechanical stress with the exception that p38 phosphorylation is reduced by metabolic stress. Supported by DC05017