Expression of c-myc and c-fos in rat skeletal muscle. Evidence for increased levels of c-myc mRNA during hypertrophy.
The levels of c-myc and c-fos mRNA were investigated in rat skeletal muscle by Northern hybridization. During post-natal development in the rat, c-myc mRNA levels were similar at birth and at 7 and 21 days of age, but then declined at 90 days and were barely detectable at 1 year. c-fos mRNA levels followed this pattern of expression until 90 days, but showed a large increase at 1 year. Hypertrophy of soleus and plantaris muscles was induced either by severance of the tendon to the synergistic gastrocnemius (tenotomy) or by administration of the beta-adrenoceptor agonist clenbuterol. In both cases hypertrophy was associated with a rapid increase in c-myc mRNA levels. Following tenotomy the increase was both greater (8-fold) and more rapid (3 h) in soleus than in plantaris (2-3 fold, 12 h). Similar effects were observed during clenbuterol administration. Neither treatment caused any alteration in c-fos mRNA levels in the plantaris muscle. The results show that increased c-myc mRNA levels are an early event in the response of skeletal muscle to hypertrophic stimuli; it is argued that this occurs within the differentiated skeletal muscle fibres.
Whitelaw
P F
PF
Division of Biochemical Sciences, Rowett Research Institute, Bucksburn, Aberdeen, U.K.
Hesketh
J E
JE
D000375:Aging; D000818:Animals; D015152:Blotting, Northern; D002976:Clenbuterol / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D016762:Genes, fos; D016259:Genes, myc / Q000187:drug effects; D006984:Hypertrophy; D024510:Muscle Development; D009132:Muscles / Q000187:drug effects / Q000473:pathology*; D012333:RNA, Messenger / Q000378:metabolism*; D012337:RNA, Ribosomal, 18S / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013710:Tendons / Q000502:physiology
D012333:RNA, Messenger; D012337:RNA, Ribosomal, 18S; D002976:Clenbuterol