Regulatory effects of insulin-like growth factors I and II on bone collagen synthesis in rat calvarial cultures.
Insulin-like growth factors I and II (IGF-I and -II) are polypeptides secreted by skeletal cells and are considered regulators of bone formation. IGF-I and -II were studied for their effects on collagen synthesis and degradation in cultures of intact fetal rat calvariae and on type I collagen transcript levels in osteoblast-enriched (Ob) cells from fetal rat parietal bone. IGF-I and -II increased [3H]proline incorporation into type I collagen independently of their effect on cell replication. IGF-I and -II also decreased collagen degradation in calvarial cultures. Both factors had similar actions, although IGF-I stimulated collagen synthesis at 10 nM, and IGF-II at 30 nM. In Ob cells, IGF-I and -II also increased [3H]proline incorporation into type I collagen, but the effect was seen at 100 nM, and neither factor decreased collagen degradation. Slot blot analysis of IGF-I- and IGF-II-treated cells, using a rat type I collagen cDNA probe, revealed an increase in type I collagen transcripts. In conclusion, IGF-I and -II increase bone collagen synthesis and decrease collagen degradation in cultures of intact calvariae; the effect on collagen synthesis correlates with an increase in transcript levels in Ob cells.
McCarthy
T L
TL
Department of Medicine (Endocrine Section), Saint Francis Hospital and Medical Center, Hartford, Connecticut 06105.
Centrella
M
M
Canalis
E
E
D000818:Animals; D015152:Blotting, Northern; D001842:Bone and Bones / Q000196:embryology / Q000378:metabolism*; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis*; D004247:DNA / Q000096:biosynthesis; D015342:DNA Probes; D004591:Electrophoresis, Polyacrylamide Gel; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D009693:Nucleic Acid Hybridization; D010006:Osteoblasts / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D013002:Somatomedins / Q000494:pharmacology*
D015342:DNA Probes; D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D003094:Collagen; D004247:DNA