Activation of insulin-like growth factor II expression during skeletal muscle regeneration in the rat: correlation with myotube formation.
Insulin-like growth factors (IGFs) are important stimulators of proliferation and differentiation of cultured myoblasts. It has previously been shown that IGF-I is induced during muscle regeneration in rodents, however, little is known about the expression of IGF-II. Therefore, two in vivo models were used to analyze IGF-II mRNA expression during skeletal muscle regeneration in the rat: injection of the snake venom notexin and induction of ischemia. During the regeneration process the levels of both IGF-I and IGF-II mRNA were transiently induced, as analyzed by solution hybridization. Both IGF-I-like immunoreactivity and IGF-II-like immunoreactivity were found to be present during muscle regeneration. In a time course study, induction of IGF-II was preceded by IGF-I, both at the mRNA and protein levels. Using alpha- and beta-actin as markers for different stages of skeletal muscle differentiation, together with the immunohistochemistry data, it is concluded that the expression of IGF-I and IGF-II occurs at different differentiation stages, and that IGF-II appears concomitant to the formation of myotubes. These results suggest that each IGF has a distinct role during the differentiation of muscle cells.
Levinovitz
A
A
Center for Biotechnology, Karolinska Institute, NOVUM, Huddinge, Sweden.
Jennische
E
E
Oldfors
A
A
Edwall
D
D
Norstedt
G
G
D000818:Animals; D015152:Blotting, Northern; D004546:Elapid Venoms; D005786:Gene Expression Regulation / Q000502:physiology; D007124:Immunoenzyme Techniques; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis; D007335:Insulin-Like Growth Factor II / Q000096:biosynthesis* / Q000235:genetics; D007511:Ischemia / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000098:blood supply / Q000473:pathology / Q000502:physiology*; D009336:Necrosis; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012038:Regeneration / Q000502:physiology*
D004546:Elapid Venoms; D012333:RNA, Messenger; C005082:notexin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II