Growth hormone and parathyroid hormone stimulate IGFBP-3 in rat osteoblasts.
Osteoblast-like cells prepared from calvaria of newborn rats produce insulin-like growth factor (IGF) I and several insulin-like growth factor binding proteins (IGFBPs) in vitro. Among the IGFBPs found in conditioned cell culture medium, IGFBP-3 is the most abundant. Intact IGFBP-3, as assessed by 125I-labeled IGF-II ligand blot analysis, is more abundant in culture media of cells exposed to growth hormone (GH) or to parathyroid hormone (PTH), both at 5 x 10(-9) mol/l, for 24 h. At the same time, concentrations of IGF-I are increased in media of cells exposed to PTH but not to GH, compared with hormone-free control cultures. IGFBP-3 mRNA is increased in osteoblasts exposed to PTH or to GH but not in response to 5 x 10(-9) mol/l IGF-I. PTH exerts a rapid (within 2 h) stimulatory effect on IGF-I and IGFBP-3 production, both at the message and peptide levels, whereas GH increases only IGFBP-3, both at the message and peptide levels (after 24 h). We conclude that IGF-I does not mediate increased IGFBP-3 production by rat osteoblasts in response to GH and PTH.
Schmid
C
C
Department of Internal Medicine, University Hospital, Zurich, Switzerland.
Schläpfer
I
I
Peter
M
M
Böni-Schnetzler
M
M
Schwander
J
J
Zapf
J
J
Froesch
E R
ER
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003470:Culture Media; D013006:Growth Hormone / Q000494:pharmacology*; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D010006:Osteoblasts / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D002352:Carrier Proteins; D003470:Culture Media; D018969:Insulin-Like Growth Factor Binding Proteins; D010281:Parathyroid Hormone; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone