Repetitive stretch induces c-fos and myogenin mRNA within several hours in skeletal muscle removed from rats.

Abstract

To investigate what effect repetitive stretch has on gene transcription in muscle tissues removed from rats. Case-control study. University laboratory. Eight female 8-week-old Wistar rats. Rat anterior tibial and soleus muscles were removed and repetitively stretched about 20% of the muscle length by using the Magnus method in Krebs-Ringer solution. Stretch-relax cycles 15 times per minute were continued for 2 hours in 1 group and 4 hours in another group. Contralateral muscles removed from the same rat were incubated without stretch as the control. After repetitive stretch, total ribonucleic acid (RNA) was extracted from the muscles and Northern blotting was carried out using c-fos and myogenin oligonucleotide as probes. Repetitive stretch during 2 hours significantly increased the expression of c-fos messenger RNA (mRNA) in both the tibialis anterior and soleus muscles. Increased expression of myogenin mRNA in both muscles was observed with repetitive stretch for 4 hours. Because of the initial increase of immediate early gene c-fos mRNA and the subsequent increase of myogenic transcription factor myogenin mRNA, it appears that repetitive muscle stretch induces sequential progression of gene transcription toward muscle hypertrophy. Mechanical repetitive stretch for a few hours would be one of the stimulating factors for muscle growth and should be available for muscle training in clinical rehabilitation.