Background: Aging leads to changes in skeletal muscle quantity and quality and is
accompanied with increase in body mass and fat mass, whereas fat-free mass either decreases or
remains unchanged. The body composition of rodents has been an important factor for clinical trials
in the laboratory. Glucocorticoids such as dexamethasone are widely used in clinical medicine, but
may induce myopathy, characterized by muscle weakness, atrophy, and fatigue. In animals treated
with glucocorticoids, a dose-dependent reduction of body weight has been observed. This weight
loss is usually followed by muscle atrophy and a reduction of several muscle proteins, contributing
to impaired muscle function. This study was designed to describe changes in body composition and
BMC of 22-month-old rats during 10- and 20-day recovery period after 10-day dexamethasone
Methods: Data on body mass, lean body mass, fat mass and bone mineral content of the rats were
obtained with dual energy X-ray absorptiometry scan.
Results: Significant reduction in body mass, lean body mass, fat mass and fast-twitch muscle mass
was observed after dexamethasone treatment. Body mass, fat mass and fast-twitch muscle mass
stayed decreased during 20 days after terminating the hormone administration; lean body mass
reached the preadministration level after 20-day recovery period. There were no significant changes
in bone mineral density during the recovery period. Dexamethasone treatment gradually reduced
hindlimb grip strength that also stayed decreased during the 20-day recovery period.
Conclusion: This study demonstrated that a 10-day period of overexprosure to glycocorticoids
induced longlasting changes in old rats’ body composition and these values did not attain the
baseline level even after 20-day recovery period.