Developmental expression and location of IGF-I and IGF-II mRNA and protein in skeletal muscle.
To investigate the role of IGF in muscle development in vivo, developmental expression and location of IGF-I and -II protein and mRNA were examined in fetal, postnatal, and adult skeletal muscle. Muscle tissue was collected from 30-, 44-, 59-, 68-, 75-, 89-, and 109-d porcine fetuses, 21-d neonatal pigs, and 6-mo-old (adult) pigs. Relative amounts of IGF-II mRNA peaked (P < .05) in 59-d fetal muscle and decreased thereafter. Inversely, muscle IGF-I expression increased (P < .05) to maximal levels around birth. For in situ hybridization, frozen muscle tissue sections (10 microm) were hybridized with a hydrolyzed form of the same riboprobes or incubated with polyclonal or monoclonal antibodies to IGF-I or -II, respectively. The majority of IGF-I and IGF-II mRNA was localized to developing muscle fibers, whereas little signal was found in the surrounding connective tissues. Immunofluorescent localization of IGF-I and -II confirmed that muscle IGF are present in developing muscle fibers. Collectively, these data show that IGF-I and -II are expressed and produced primarily in muscle cells within developing muscle tissue and support the hypothesis that IGF-I and -II modulate fetal muscle development.
Gerrard
D E
DE
Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
Okamura
C S
CS
Ranalletta
M A
MA
Grant
A L
AL
D000818:Animals; D015152:Blotting, Northern / Q000662:veterinary; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D005865:Gestational Age; D017403:In Situ Hybridization / Q000662:veterinary; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000235:genetics*; D007335:Insulin-Like Growth Factor II / Q000032:analysis / Q000235:genetics*; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000196:embryology; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D013552:Swine / Q000196:embryology / Q000254:growth & development*
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II