1. ¹Department of Physical Therapy, Texas Women's University, Houston, Texas, TX 77030, USA
2. ²Department of Physical Therapy, The University of Florida, Gainesville, Florida, FL 32610, USA
3. ³Veterans Affairs Administration, UMDNJ-New Jersey Medical School, Newark, New Jersey, NJ 07018, USA
4. ⁴Department of Exercise Science, The University of Georgia, Athens, Georgia, GA 30602, USA

Correspondence: G Alton Dudley, Department of Exercise Science, The University of Georgia, 115 Ramsey Student Center, 300 River Road, Athens, Georgia, GA 30602-3654, USA

Abstract

Study design: Randomized control.

Objective: To examine the effects of testosterone replacement therapy (TRT) on skeletal muscle 11 weeks after complete SCI.

Setting: Athens, Georgia USA.

Methods: Soleus (SOL), gastrocnemius (GA), tibialis anterior (TA), vastus lateralis (VL) and triceps brachii (TRI) muscles were taken from twelve young male Charles River rats 11 weeks after complete SCI (T-9 transection, n=8) or sham surgery (n=4). Rats received either TRT (two 5 cm capsules, n=4) or empty capsules (n=8) implanted at surgery. Muscle samples were sectioned and fibers analyzed qualitatively for myosin ATPase and quantitatively for succinate dehydrogenase (SDH), -glycerol-phosphate dehydrogenase (GPDH) and actomyosin ATPase (qATPase) activities using standard techniques.

Results: SCI decreased average fiber size (494%) in affected muscles and the percentage of slow fibers in SOL (933% to 172%). In addition, there was a decrease in SDH and an increase in GPDH and qATPase activities across the four hind-limb muscles of the SCI animals. Fiber size in the TRI was increased (312%) by SCI while enzyme activities were not altered. Average fiber size across the four hind limb muscles was decreased by only 30% in TRT SCI animals and their SOL contained 392% slow fibers. TRT also attenuated changes in enzyme activities. There was no effect of TRT on the TRI relative to SCI.

Conclusions: TRT was effective in attenuating alterations in myofibrillar proteins during 11 weeks of SCI in affected skelatal muscles.

Sponsorship: Supported by a grant from The National Institutes of Health (HD-33738) and HD-37645 to KV, and HD-39676 to GAD.