Autocrine regulators of MC3T3-E1 cell proliferation.
MC3T3-E1 cells, a clonal osteoblast-like mouse calvarial cell line, secrete several growth regulating factors. These regulators include insulin-like growth factor (IGF) type I, transforming growth factor beta (TGF-beta), and IGF-II in descending order of abundance. MC3T3-E1 cells in culture also produce two IGF binding proteins (IGFBP), M(r) 25 and 32 kD, having sequence identity with IGFBP-4 and IGFBP-6, respectively. In addition, this is the first observation that osteoblast-like bone cells in culture produce IGFBP-6. To determine if growth factors produced by MC3T3-E1 cells have autocrine actions on these cells, the effects of IGF-I, IGF II, TGF-beta 1, and IGFBP-4 on MC3T3-E1 cell proliferation were determined. Exogenous addition of IGF-I and IGF-II stimulated MC3T3-E1 cell proliferation, but TGF-beta 1 and IGFBP-4 inhibited MC3T3-E1 cell proliferation. Based on these findings, we conclude that MC3T3-E1 cells in culture produce autocrine regulators of MC3T3-E1 cell proliferation and that the actions of IGFs may also be regulated by IGFBPs produced by these same cells.
Amarnani
S
S
Department of Medicine, Loma Linda University, California.
Merriman
H L
HL
Linkhart
T A
TA
Baylink
D J
DJ
Mohan
S
S
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000096:biosynthesis / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D017077:Culture Media, Conditioned; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000096:biosynthesis / Q000494:pharmacology*; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011863:Radioimmunoassay; D011869:Radioligand Assay; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000494:pharmacology*
D002352:Carrier Proteins; D017077:Culture Media, Conditioned; D018969:Insulin-Like Growth Factor Binding Proteins; D016212:Transforming Growth Factor beta; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II