Introduction
Resistance and endurance training are known to induce different muscular adaptations. While the physiologic responses that result from these modes of exercise have been well characterized (Holloszy & Coyle, 1984, Tesch 1987), the molecular events underlying such adaptations remain poorly defined. Among these events, several signaling pathways are beginning to be elucidated some of which are known to regulate gene transcription (Seger & Krebs, 1995) and mRNA translation (Jeffries & Thomas 1996).
Methods
To gain insight into the potential molecular mechanisms regulating exercise-induced adaptations, we studied intracellular signaling pathways in rat skeletal muscle in response to previously characterized high resistance (Baar & Esser 1999), low resistance (Patel et al. 1998) and running (Divine-Patch & Brooks 1990) exercise protocols. The phosphorylation states of several signaling molecules were analyzed in the tibialis anterior and soleus muscles at 0, 3 and 6 hrs. post-exercise.
Results
When exercise protocols were compared, a different pattern of phosphorylation was found in the Extracellular Regulated kinase (ERK), p38 kinase (p38), Protein kinase B (PKB), and p70 S6 kinase (p70S6k). Different patterns were also observed when muscles within exercise modes were analyzed. Interestingly, the differences observed were not only significant in their magnitude, but also in a time dependent manner.
Conclusions
Taken together our results suggest that multiple signaling pathways are initially activated by exercise and that this activation is specific to the muscle(s) used and to the different modes of exercise.
Supported by NIH AR 45617.
References
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Divine Patch, L. & Brooks, G. A. 1990. Pflügers Arch. 386: 215-219.
Jeffries, H.B.J & Thomas, G. 1996. In: Hershey, J.W.B., Mathews, M.B. and Sonenberg, N. (eds) Translational Control, pp. 389-409. Cold Spring Harbor Laboratory Press, New York.
Holloszy, J.O. & Coyle, E.F. 1984. J. Appl. Physiol. 56: 831-838, 1984.
Patel, T. J., Cuizon, D., Mathieu-Costello, O., Fridén, J. & Lieber, R. 1998. Am. J. Physiol. 274:R1300-R1308, 1998.
Seger, R. & Krebs, E. 1995. Faseb J. 9:726-735.
Tesch, P. 1987. In: M. Hebbelinck and Shepard, R.J. (eds) Medicine Sport Sci., pp. 67-89. S. Karger, Basel.