Effects of melatonin on skeletal muscle of rats with experimental hyperthyroidism

The aim of this study was to investigate structural changes that occurred in the skeletal muscle of rats with experimental hyperthyroidism and the effect of melatonin on these changes. Groups of animals were designated as controls, 3,3',5-triiodothyronine (T3) injected and T3 + melatonin injected group. At the end of the study the tissue specimens were harvested and their structure examined. In the skeletal muscle of T3 injected rats a decrease was observed in muscle fiber diameter, splitting of fiber, collections of adipose tissue in perimysium, and gathering of nuclei in central compared to the control. Electron microscopic examination showed that mitochondria were dilated and the I band was less clear. In the T3 + melatonin injected group, the structure of fibers was similar to control. In conclusion, this study showed that T3 injection caused structural changes in the skeletal muscle and that melatonin had a positive effect on these changes.