The expressions of insulin-like growth factors, their receptors, and binding proteins are related to the mechanism regulating masseter muscle mass in the rat.
OBJECTIVE
The mechanism regulating skeletal muscle mass is unclear. The purpose of the present study was to investigate the extent to which insulin-like growth factors (IGFs), their receptors (IGFRs), and binding proteins (IGFBPs) are involved in the regulation of skeletal muscle mass.


METHODS
We measured the mRNA expression levels for IGFs, IGFRs, and IGFBPs in the rat masseter muscle hypertrophied by oral administration of clenbuterol for 3 weeks and determined the correlations between the weight of masseter muscle and the mRNA expression levels.


RESULTS
The mRNA expression levels for IGF-I and II, IGFR1 and 2, and IGFBP4 and 6 showed clenbuterol-induced elevations and positive correlations with the weight of masseter muscle. That for IGFBP3 only exhibited a clenbuterol-induced decrease and a strong negative correlation with the weight of masseter muscle. The mRNA expression levels for IGFBP2 and 5 showed no significant changes between the control and clenbuterol groups, and no significant correlations. IGFBP1 mRNA was not detectable.


CONCLUSIONS
These results suggest that IGF-I, II, IGFR1 and 2, and IGFBP3, 4 and 6 are related to the mechanism regulating masseter muscle mass in the rat.
Matsumoto
T
T
Department of Geriatric Dentistry, Tsurumi University School of Dental Medicine, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230-8501, Japan.
Akutsu
S
S
Wakana
N
N
Morito
M
M
Shimada
A
A
Yamane
A
A
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002976:Clenbuterol / Q000494:pharmacology; D006984:Hypertrophy / Q000139:chemically induced; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism*; D008297:Male; D008406:Masseter Muscle / Q000033:anatomy & histology / Q000187:drug effects* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017451:Receptors, Somatomedin / Q000378:metabolism*; D013002:Somatomedins / Q000378:metabolism*
D000318:Adrenergic beta-Agonists; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D017451:Receptors, Somatomedin; D013002:Somatomedins; D002976:Clenbuterol