Triiodothyronine (T3) stimulates insulin-like growth factor (IGF)-1 and IGF binding protein (IGFBP)-2 production by rat osteoblasts in vitro.
Osteoblast-like cells prepared from neonatal rat calvariae and grown under serum-free conditions produce IGF-1 and IGFBPs. In contrast to growth hormone, T3 and PTH increased both IGF-1 mRNA expression and net IGF-1 release in calvaria cells. In addition, they stimulated net production of IGFBP-3 and of an IGFBP with an apparent molecular weight of 32 kDa which was recognized by an antiserum against rat IGFBP-2. Bone cells expressed remarkably high levels of mRNA for IGFBP-2, the predominant IGFBP in serum of newborn rats. T3 at low physiological concentrations but not growth hormone stimulated IGFBP-2 mRNA expression and IGFBP-2 production in bone cells in vitro. Thus, IGFBPs are differentially regulated by these hormones and may play an autocrine/paracrine regulatory role in bone.
Schmid
C
C
Department of Internal Medicine, University Hospital, Zürich, Switzerland.
Schläpfer
I
I
Futo
E
E
Waldvogel
M
M
Schwander
J
J
Zapf
J
J
Froesch
E R
ER
D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D013006:Growth Hormone / Q000494:pharmacology; D007016:Hypophysectomy; D018971:Insulin-Like Growth Factor Binding Protein 2; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D008970:Molecular Weight; D010006:Osteoblasts / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D013002:Somatomedins / Q000096:biosynthesis; D014284:Triiodothyronine / Q000494:pharmacology*
D002352:Carrier Proteins; D018971:Insulin-Like Growth Factor Binding Protein 2; D010281:Parathyroid Hormone; D012333:RNA, Messenger; D013002:Somatomedins; D014284:Triiodothyronine; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone