Testosterone and Ca2+ regulation in skeletal muscle

Area of Science:

• Exercise Physiology
• Molecular Biology
• Muscle Physiology

Background:

• Testosterone influences skeletal muscle function and adaptation.
• Exercise training is known to increase plasma testosterone levels.
• Understanding receptor expression changes is crucial for muscle adaptation.

Purpose of the Study:

• To investigate the impact of testosterone treatment on dihydropyridine and ryanodine receptor expression in mouse skeletal muscle.
• To compare the effects of testosterone administration with those of treadmill training on these receptors and myosin heavy chain phenotypes.

Main Methods:

• Male mice were subjected to either testosterone administration or treadmill training for 6 weeks.
• Hindlimb muscles were analyzed for dihydropyridine and ryanodine receptor expression using Western blotting.
• Myosin heavy chain phenotypes were also assessed.

Main Results:

• Both testosterone and training altered receptor expression and myosin composition.
• Testosterone treatment increased dihydropyridine receptors in extensor digitorum longus but decreased them in soleus; ryanodine receptors increased in rectus femoris and plantaris.
• Training significantly increased ryanodine receptor expression across multiple muscles (gastrocnemius, soleus, plantaris, extensor digitorum longus) with no observed changes in dihydropyridine receptors.

Conclusions:

• Exercise training demonstrates a more substantial role in skeletal muscle adaptation than elevated plasma testosterone levels alone.
• Both interventions had comparable effects on postural muscles.
• These findings highlight the distinct and overlapping molecular adaptations induced by hormonal changes versus physical activity.