Ultrasonographic evaluation of gastrocnemius muscle in a rat model of N-methyl-N-nitrosourea-induced mammary tumor.

BACKGROUND/AIM: Ultrasonography is frequently used to study body tissues. Our aim was to evaluate by ultrasonography, gastrocnemius muscle wasting induced by cancer in a rat model of chemically-induced mammary tumor, muscular response to exercise. MATERIALS AND METHODS: Female Sprague-Dawley rats were divided into as well as four groups. Groups I and II were injected with N-methyl-N-nitrosourea (MNU). Groups I and III performed endurance training on a treadmill. Gastrocnemius muscles were palpated for tonus evaluation. Gastrocnemius muscle and fibrous tissue between muscle and tibia were examined by ultrasonography. At necropsy, muscle was collected and weighed. Myostatin was assessed by immunoblotting. RESULTS: The final body weight, gastrocnemius weight, length and width were similar among groups. Tone of muscle was higher in exercised animals. Myostatin was higher in MNU-treated groups. Echogenicity of muscle and fibrous tissue in group IV was higher than in other groups (p<0.05). Echogenicity of fibrous tissue was higher than echogenicity of muscle in all groups. CONCLUSION: Our results showed that muscle ultrasonography is a useful tool to identify alterations in muscle structure. More studies are necessary for researchers to understand the influence of fat location in muscle ultrasonographic imaging.