Growth hormone induces CCAAT/enhancer binding protein alpha (C/EBPalpha) in cultured rat hepatocytes.
OBJECTIVE
The transcription factor CCAAT/enhancer binding protein alpha (C/EBPalpha) is a transactivator of several genes in the liver, which are regulated by growth hormone.


METHODS
Growth hormone (100 ng/ml) was added to primary rat hepatocytes cultured on a laminin-rich matrix. C/EBP mRNA and protein levels were measured by RNase protection assay and Western blotting, respectively. DNA binding activity was measured by electrophoretic mobility shift assay (EMSA).


RESULTS
Growth hormone treatment for 6 h to 3 days increased C/EBPalpha mRNA levels. Addition of growth hormone for 24 h and 4 days also enhanced the levels of the 42 and 30 kDa isoforms of immunoreactive C/EBPalpha. EMSA showed that addition of growth hormone for 24 h enhanced the abundance of a protein complex binding to a consensus C/EBP binding DNA oligonucleotide. This protein complex was supershifted by antibodies directed against C/EBPalpha but not against C/EBPbeta. There were no consistent effects on C/EBPbeta mRNA or protein at any timepoint. The growth hormone effect on C/EBPalpha expression was not affected by simultaneous incubation with insulin or glucocorticoids, two hormones that previously have been reported to affect C/EBPs.


CONCLUSIONS
Growth hormone enhances the levels of C/EBPalpha mRNA and protein as well as the DNA binding activity of C/EBPalpha in cultured rat hepatocytes.
Strand
P
P
RCEM, Department of Internal Medicine, Sahlgrenska University Hospital, Göteborg, Sweden.
Carlsson
L
L
Rask
K
K
Skrtic
S
S
Ekberg
S
S
Hedin
L
L
Oscarsson
J
J
Jansson
J O
JO
D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology*; D006801:Humans; D008099:Liver / Q000378:metabolism*; D009687:Nuclear Proteins / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D013006:Growth Hormone; D004247:DNA