Disuse of a limb has been repeatedly demonstrated to cause pronounced atrophy of skeletal muscle. In animals and humans, disuse of a leg due to immobilization can cause pronounced catabolism of many skeletal muscle proteins. Strength, V02 max, oxidative enzyme activities, protein synthesis, and muscle weight are all diminished due to chronic limb immobilization.Testosterone is classified as an anabolic steroid which has the effect of increasing protein synthesis in many tissues. Recently, testosterone has been shown to have a definite anti-catabolic effect on skeletal muacle by competing with glucocorticoids for binding proteins within the muscle cell. This reduces the effect of the circulating catabolic hormones. By slowing protein breakdown and increasing protein synthesis in the skeletal muscle of an immobilized limb, testosterone could effectively delay the rapid atrophy so often seen.To examine the effects of testosterone on skeletal muscle atrophy during limb immobilization, forty albino, male rats were randomly divided into four groups of ten. Group I served as the non-immobilized control and received daily placebo injections of sesame oil. The rats in group II were castrated and their hindlimbs were immobilized using a plaster cast. The animals in this group also received daily injections of sesame oil. The group III rats were also castrated and casted, but they received a daily injection of 5 mg testosterone propionate. The animals in group IV were not castrated but were casted.These rats also received a daily injection of testosterone. The duration of treatment was two weeks for each rat. Body weights were measured before and after treatment. The gastrocnemius, quadriceps, soleus, and cardiac muscles were weighed after treatment. Oxygen consumption capacity (Q02), citrate synthase activity, total protein, and percentage of water were also measured in the gastrocnemius, quadriceps, and cardiac tissues.The results of this study demonstrate that hindlimb immobilization not only causes severe atrophy in those muscles immobilized, but has an overal catabolic effect on the animal. Along with the effects on muscle and body size, the immobilization also significantly reduced the aerobic capacity of affected muscle groups and cardiac tissue. The study also gave evidence that testosterone, or the lack of it, can affect the rate of muscle atrophy. The greatest reduction in body weight, muscle size, heart size, and QO2 were seen in the castrated group which only received a placebo injection of sesame oil. The anti-catabolic effect of testosterone was evedent in groups III and IV.
| Identifer | oai:union.ndltd.org:BSU/oai:cardinalscholar.bsu.edu:handle/176100 |
| Date | 03 June 2011 |
| Creators | Evans, William J. |
| Contributors | Bennett, Alice |
| Source Sets | Ball State University |
| Detected Language | English |
| Format | vi, 51 leaves : ill. ; 28 cm. |
| Source | Virtual Press |
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