PhD defence - Martin Thomassen

Regulation of Na+/K+ pump activity and importance of skeletal muscle ion transporting proteins for performance in humans

Development of muscular fatigue in human skeletal muscles during exercise is a complex phenomenon. Disturbances in ion homeostasis around the muscle membrane and particular accumulation of K+ in the interstitium can induce membrane depolarization and thereby affect the ability to perform intense work. Thus, the expression of the ion transporting proteins in skeletal muscles seems to be of importance for human muscle cells in order to control ion homeostasis and postpone development of muscle fatigue in relation to intense exercise.

The present PhD thesis has primarily focused on interventions able to manipulate with the expression of proteins involved in ion regulation. Treatment with dexamethasone as well as different training and inactivity regimes has been successfully used for this purpose. Effects of ion regulation during intense exercise on muscle fatigue development and exercise performance has been examined. Furthermore, molecular mechanisms involved in the regulation of Na+/K+ pump activity in the transition from rest to exercise is addressed in the thesis.

Results from the included experiments show a connection between alterations in FXYD1 phosphorylation and the exercise induced increase in human skeletal muscle Na+/K+ pump activity. As well, changes in the expression of proteins involved in ion transport across muscle membranes and especially K+ regulation seems to affect performance of intense exercise.


Tuesday March 30 2010 at 14.00 o'clock


Auditorium 1, August Krogh building, Universitetsparken 13, 2100 Copenhagen Ø


Professor Ole Bækgaard Nielsen, Department of Physiology and Biohysics, Faculty of Health Sciences, Aarhus University, Denmark

Associate professor Alexander V. Chibalin, Section of Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institute, Sweden

Associate professor Bente Rona Jensen, Department of Exercise and Sport Sciences, University of Copenhagen, Denmark (chairman)


Professor Jens Bangsbo, Department of Exercise and Sport Sciences, Faculty of Science, University of Copenhagen, Denmark