Growth hormone regulates the level of insulin-like growth factor-I mRNA in rat skeletal muscle.
Levels of mRNA for the insulin-like growth factor-I (IGF-I) in rat heart and skeletal muscle and its dependence on GH were investigated using a solution hybridization assay. Levels of IGF-I mRNA decreased following hypophysectomy, and replacement therapy with human GH (hGH) normalized heart and skeletal muscle levels. The stimulatory effect of hGH was dose-dependent, the lowest effective dose being 100 micrograms. A significant increase of IGF-I mRNA was observed 60 min after s.c. administration of 100 micrograms hGH and the maximum increase was apparent 6-12 h after hGH injection. Administration of 200 micrograms IGF-I or 11 micrograms insulin did not significantly change levels of IGF-I mRNA. The results show that GH regulates the level of IGF-I mRNA in rat heart and skeletal muscle and give further support to the hypothesis that locally produced IGF-I might be a local mediator for the direct stimulatory effect of GH on the growth and development of heart and skeletal muscle.
Isgaard
J
J
Department of Physiology, University of Göteborg, Sweden.
Nilsson
A
A
Vikman
K
K
Isaksson
O G
OG
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D013006:Growth Hormone / Q000494:pharmacology*; D007016:Hypophysectomy; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008297:Male; D009206:Myocardium / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013002:Somatomedins / Q000235:genetics*; D013997:Time Factors
D001786:Blood Glucose; D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone