Effects of steroids on diaphragmatic function in rats

Area of Science:

• Physiology
• Pharmacology
• Muscle Biology

Background:

• Corticosteroids are widely used clinically but can cause muscle atrophy.
• The diaphragm, crucial for respiration, may be susceptible to corticosteroid-induced myopathy.

Purpose of the Study:

• To investigate the impact of short-term corticosteroid administration on diaphragmatic atrophy and contractile function.
• To compare the effects of corticosteroids on the diaphragm versus limb muscles (soleus and extensor digitorum longus).

Main Methods:

• Rats received a single corticosteroid injection (Kenacort 80 retard) or placebo for 8 days.
• Body weight, diaphragmatic mass, and limb muscle weights were measured.
• In vivo and in vitro contractile properties of the diaphragm and limb muscles were assessed using electrophysiological stimulation.

Main Results:

• Steroid treatment led to a 30% decrease in body weight and proportional reduction in diaphragmatic and extensor digitorum longus (EDL) muscle mass.
• Normalized tetanic force of the diaphragm significantly decreased (p < 0.001) in steroid-treated rats.
• Twitch and low-frequency diaphragm forces were unaffected, while EDL showed a minor 11% reduction in tetanic tension.

Conclusions:

• Eight days of corticosteroid administration induces significant diaphragmatic atrophy and impairs its contractile force.
• The diaphragm appears more sensitive to corticosteroid-induced myopathy than the soleus muscle, with moderate effects on the EDL.
• These findings underscore the potential for respiratory muscle dysfunction with corticosteroid therapy.