The temporal and cellular expression of c-fos and c-jun in mechanically stimulated rabbit latissimus dorsi muscle.
The levels of c-fos and c-jun mRNA were measured by reverse transcription PCR in the rabbit latissimus dorsi muscle following three separate training regimes, i.e. passive stretch, 10 Hz electrical stimulation or a combination of the two. Both c-fos and c-jun mRNA expression peaked at around 1 h after imposing stretch and at around 4.5-6 h after the initiation of electrical stimulation. The combined stretch/electrical stimulation regime induced biphasic expression of both c-fos and c-jun mRNA, with peaks coinciding temporally with those for the individual regimes. Immunostaining with anti-Fos and anti-Jun antibodies revealed the accumulation of these proteins in both myofibre and interstitial cell nuclei following passive stretch. In contrast, following electrical stimulation the localization of immunoreactive c-Fos and c-Jun proteins was predominantly in interstitial cell nuclei. c-Fos and c-Jun immunoreactivity was also clearly colocalized in a proportion of myonuclei from stretched muscle. These findings suggest that the rapid induction of c-fos and c-jun is an early event in response to mechanical stretch and might trigger [via activator protein-1 (AP-1) transcriptional factors] events leading to muscle fibre hypertrophy. However, the involvement of AP-1 in inducing the phenotypic changes in muscle fibres as a result of electrical stimulation appears less clear.
Osbaldeston
N J
NJ
Department of Clinical Medicine, University of Leeds, U.K.
Lee
D M
DM
Cox
V M
VM
Hesketh
J E
JE
Morrison
J F
JF
Blair
G E
GE
Goldspink
D F
DF
D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D004558:Electric Stimulation; D005786:Gene Expression Regulation; D016762:Genes, fos; D016758:Genes, jun; D008969:Molecular Sequence Data; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D013314:Stress, Mechanical; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism*
D017931:DNA Primers; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D018808:Transcription Factor AP-1