Isolation and characterization of insulin-like growth factor I (somatomedin-C) from cultures of fetal rat calvariae.
Cultured bones have been shown to secrete local regulators of bone remodeling, such as beta 2-microglobulin, transforming growth factor-beta, and insulin-like growth factor (IGF), but the IGF secreted has not been characterized. In the present study, IGF from medium conditioned by 21-day-old fetal rat calvariae was isolated and characterized. IGF was purified using dialysis, gel filtration, and reverse phase HPLC. Amino acid composition was compatible with that of IGF I (somatomedin-C), and amino-terminal sequence analysis revealed homology with IGF-I. The concentration of IGF-I in the calvarial culture medium was 1 nM and was suppressed by cycloheximide. Calvaria-derived rat IGF I at 20 nM stimulated DNA and collagen synthesis by 42% and 26%, respectively, in monolayer cultures of osteoblast-rich rat parietal bone cells. This study indicates that locally produced IGF-I regulates bone formation in cultures of 21-day-old fetal rat calvariae.
Canalis
E
E
Department of Medicine (Endocrine Section), Saint Francis Hospital and Medical Center, Hartford, Connecticut 06105.
McCarthy
T
T
Centrella
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001842:Bone and Bones / Q000032:analysis / Q000196:embryology*; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D005333:Fetus; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000302:isolation & purification*; D051381:Rats; D013002:Somatomedins / Q000302:isolation & purification*; D013045:Species Specificity
D013002:Somatomedins; D007334:Insulin-Like Growth Factor I