Growth hormone plus resistance exercise attenuate structural changes in rat myotendinous junctions resulting from...

Area of Science:

• Muscle physiology
• Cellular biology
• Biomechanics

Background:

• Myotendinous junctions (MTJs) transmit muscle forces to the extracellular matrix.
• MTJ structure involves highly folded sarcolemma and extracellular matrix interfaces.
• Muscle unloading causes structural changes at the MTJ.

Purpose of the Study:

• To investigate the effects of exercise and growth hormone (GH) on MTJ structure during muscle unloading.
• To determine if combined exercise and GH can counteract unloading-induced adaptations.

Main Methods:

• Utilized hypophysectomized rats subjected to hindlimb unloading for 10 days.
• Administered exercise (ladder climbing) and/or GH injections.
• Analyzed plantaris muscle MTJ structure using electron microscopy.
• Quantified MTJ contact via the interface length/base (IL/B) ratio.

Main Results:

• Unloading significantly reduced the IL/B ratio compared to controls.
• Exercise or GH alone partially mitigated the reduction in IL/B ratio.
• Combined exercise and GH treatment maintained the IL/B ratio similar to controls.

Conclusions:

• Exercise and GH treatments interact to attenuate MTJ structural changes from chronic unloading.
• Combined therapy serves as a potential countermeasure against muscle unloading adaptations.
• Preserving MTJ integrity is vital for maintaining muscle function during unloading.