Poster 90: Expression of Muscular Growth Factor on Passive Stretching in the Rat Skeletal Muscle

Abstract

Objective: To investigate the effect of muscle growth by passive stretching exercise on the rat skeletal muscle. Design: Case-control study. Setting: University laboratory. Animals: 10 male Wistar rats weighing 250 to 350g. Intervention: Continuous passive stretching of unilateral gastrocnemius muscle under anesthesia by ankle dorsiflexion for 15 minutes a day, and 4 procedures were done within the week. Then muscles were removed and ribonucleic acid (RNA) was extracted. Main Outcome Measure: Semiquantitation of the messenger RNA was done for the mechanogrowth factor, that is, an autocrine variant of insulin-like growth factor secreted from muscle, and myogenin, a myogenic transcription factor that enhances the gene expression of the muscle, using the reverse transcription polymerase chain reaction method. Results: Messenger RNA of the mechanogrowth factor was significantly increased in stretched gastrocnemius muscle as compared with the unstretched contralateral one. The expression of myogenin messenger RNA trend to increase, however, the difference was not significant. Conclusions: Brief passive stretching exercise induces the mechanogrowth factor. This finding suggests that passive stretching may prevent the disuse atrophy of patients in an unconscious state or with neurologic defects.