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The uremic environment and muscle dysfunction in man and rat
A P Harrison1, A H Nielsen, I Eidemak
1Institute of Anatomy and Physiology, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark. adh@kvl.dk
Nephron. Physiology
|December 15, 2005
Summary
Uremic solutes rapidly induce muscle weakness, particularly in fast-twitch muscles, which is reversed by hemodialysis. This study investigated muscle function changes in end-stage renal disease patients and rat models.
Area of Science:
- Nephrology
- Muscle Physiology
- Electrophysiology
Background:
- End-stage renal disease (ESRD) causes debilitating fatigue and dysfunction.
- Uremic toxins are implicated in muscle weakness experienced by ESRD patients.
Purpose of the Study:
- To investigate the impact of uremic solutes on muscle function.
- To assess the reversibility of muscle dysfunction following hemodialysis.
- To compare the effects of uremia on fast-twitch versus slow-twitch muscles.
Main Methods:
- In vivo surface electromyography (EMG) measured muscle function in 25 ESRD patients before and after hemodialysis (HD).
- In vitro studies used isolated rat muscles incubated in normal or uremic conditions (rat uremic: RU; human uremic: HU).
Main Results:
- Hemodialysis significantly reduced urea, creatinine, potassium, and phosphate levels in patients.
- EMG frequency improved in fast-twitch muscles (2nd dorsal interosseous) post-HD, but not in slow-twitch muscles (vastus lateralis).
- In vitro, uremic conditions caused a faster decline in force in fast-twitch rat muscles (extensor digitorum longus) but not slow-twitch muscles (soleus).
Conclusions:
- Muscle weakness and electrophysiological changes are rapidly induced by uremic solutes and reversed by dialysis.
- Fast-twitch muscles are more susceptible to the detrimental effects of uremic conditions than slow-twitch muscles.