Insulinlike growth factor 1 regulates mRNA levels of osteonectin and pro-alpha 1(I)-collagen in clonal preosteoblastic calvarial cells.
A nontransformed rat clonal cell line (UMR-201) with phenotypic characteristics of osteoblastic precursor cells was found to respond to insulinlike growth factor 1 (IGF-1) by increased osteonectin and pro-alpha 1(I)-collagen mRNA expression. Cells were treated for 24 h with insulin, growth hormone, or IGF-1 to study the regulation of messenger RNA for osteonectin and pro-alpha 1(I)-collagen using Northern blot hybridization. UMR-201 cells possess specific high-affinity receptors for growth hormone, although there were no significant effects of growth hormone (10(-9)-10(-7) M) or insulin (10(-9)-10(-6) M) on mRNA species for osteonectin or pro-alpha 1(I)-collagen. However, IGF-1 increased both mRNA species from a concentration of 10(-9) M. The effect on osteonectin mRNA expression was likely due to increased transcription; when 5' flanking osteonectin (ON) genomic fragments were linked to the bacterial reporter gene chloramphenicol acetyltransferase (CAT) and introduced by transfection into UMR-201 cells, the transcriptional activity of the ON-CAT construct was increased 235 and 270% by 10(-8) and 10(-7) M IGF-1, respectively. In contrast, growth hormone did not change the transcriptional activity of the ON-CAT construct. In confirmation of other work, transforming growth factor beta (TGF-beta, 0.1-2.5 ng/ml) increased mRNA for osteonectin and pro-alpha 1(I)-collagen in a dose-dependent manner. Transforming growth factor alpha (TGF-alpha) at 0.1-10 ng/ml had no consistent effects in repeated experiments on osteonectin and pro-alpha 1(I)-collagen mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
Thiebaud
D
D
Department of Medicine, University of Melbourne Victoria, Australia.
Ng
K W
KW
Findlay
D M
DM
Harker
M
M
Martin
T J
TJ
D000818:Animals; D015152:Blotting, Northern; D002460:Cell Line; D002999:Clone Cells; D004247:DNA / Q000235:genetics; D013006:Growth Hormone / Q000502:physiology; D007328:Insulin / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D010006:Osteoblasts / Q000502:physiology*; D015676:Osteonectin / Q000235:genetics*; D011347:Procollagen / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D012886:Skull / Q000166:cytology; D013002:Somatomedins / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection / Q000235:genetics
D007328:Insulin; D015676:Osteonectin; D011347:Procollagen; D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D004247:DNA