Effects of dexamethasone on the production of insulin-like growth factor-I and insulin-like growth factor binding proteins in primary cultures of rat hepatocytes.
The effects of dexamethasone (Dex) on insulin-like growth factor (IGF)-I and IGF binding protein (IGFBP)-1 production were investigated in primary cultures of rat hepatocytes. Dex enhanced the secretion of IGFBP-1 as measured by ligand blot analysis but did not show any prominent effect on immunoreactive IGF-I secretion. EC50 of Dex on IGFBP-1 secretion was calculated to be 3 x 10(-8) M. The content of IGFBP-1 mRNA in the cells increased greatly in the presence of Dex but the IGF-I mRNA content did not change significantly under the same conditions. Insulin showed the opposite effect of Dex by decreasing the production of IGFBP-1 and the cellular content of IGFBP-1 mRNA. This effect of insulin was observed also with Dex in the medium. These results show that the gene expression of IGF-I and IGFBP-1 is differently regulated by glucocorticoids and insulin in primary cultures of rat hepatocytes. The results most possibly explain the in vivo effects of glucocorticoids and insulin in regulation of IGF-I and IGFBP-1 production by liver.
Miura
Y
Y
Department of Agricultural Chemistry, Faculty of Agriculture, University of Tokyo, Japan.
Higashi
Y
Y
Kato
H
H
Takahashi
S
S
Noguchi
T
T
D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology; D018970:Insulin-Like Growth Factor Binding Protein 1; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D051381:Rats
D002352:Carrier Proteins; D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D003907:Dexamethasone