Transcriptional Regulation of CYP2B1 Induction in Primary Rat Hepatocyte Cultures: Repression by Epidermal Growth Factor Is Mediated via a Distal Enhancer Region

2004 ◽  
Vol 65 (1) ◽  
pp. 172-180 ◽  
Author(s):  
Daniel Bauer ◽  
Nils Wolfram ◽  
Georg F. Kahl ◽  
Karen I. Hirsch-Ernst
Keyword(s):  
Transcriptional Regulation ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Distal Enhancer ◽  
Rat Hepatocyte ◽  
Enhancer Region ◽  
Hepatocyte Cultures ◽  
Epidermal Growth

scholarly journals Epidermal growth factor counteracts the glycogenic effect of insulin in parenchymal hepatocyte cultures

1987 ◽  
Vol 247 (2) ◽  
pp. 307-314 ◽  
Author(s):  
M H Chowdhury ◽  
L Agius
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Epithelial Cells ◽  
Cyclic Amp ◽  
Glycogen Metabolism ◽  
Metabolic Effects ◽  
Hepatocyte Cultures ◽  
Glucose Incorporation ◽  
Epidermal Growth ◽  
Parenchymal Hepatocytes

Rat parenchymal hepatocytes in monolayer culture were used to study the metabolic effects of epidermal growth factor (EGF) and insulin on ketogenesis, gluconeogenesis and glycogen metabolism. EGF, unlike insulin, did not inhibit ketogenesis from palmitate or gluconeogenesis from pyruvate in hepatocyte cultures. It also had no effect on these pathways in the presence of insulin. In contrast, EGF potently counteracted the stimulation of [14C]pyruvate incorporation into glycogen by insulin, and also glycogen deposition from both gluconeogenic precursors and glucose. The EGF concentration causing half-maximal effect was about 0.1 nM. The anti-glycogenic effect of EGF was observed after both long-term (24 h) and short-term (1 h) exposure to EGF, and was more marked in the presence of insulin than in its absence. EGF did not displace bound insulin, suggesting that it neither competes for the insulin receptor nor affects the affinity of the receptor for insulin. EGF did not alter cellular cyclic AMP; and inhibition of cyclic AMP phosphodiesterase activity did not prevent the anti-glycogenic effect of EGF. In liver-derived dividing epithelial cells, Hep-G2 cells and fibroblasts, which have no capacity for gluconeogenesis, EGF did not counteract the stimulatory effect of insulin on [14C]glucose incorporation into glycogen, and in the epithelial cells EGF increased [14C]glucose incorporation into glycogen. The counter-effect of EGF on the glycogenic action of insulin in parenchymal hepatocytes may be due to a direct effect on glycogen metabolism or to an interaction with the post-receptor events in insulin action.

scholarly journals The early stimulation of glycolysis by epidermal growth factor in isolated rat hepatocytes is secondary to the glycogenolytic effect

1995 ◽  
Vol 308 (3) ◽  
pp. 889-894 ◽  
Author(s):  
I Quintana ◽  
M Grau ◽  
F Moreno ◽  
C Soler ◽  
I Ramírez ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Rat Hepatocytes ◽  
Rat Hepatocyte ◽  
Isolated Rat Hepatocytes ◽  
End Products ◽  
Glycogenolytic Effect ◽  
Free Glucose ◽  
Epidermal Growth ◽  
Stimulation Of

We have studied the relationship between the effect of epidermal growth factor (EGF) on glycogen metabolism and its effect on glycolysis, in rat hepatocyte suspensions. Although 10 nM glucagon or 10 microM adrenaline increased glycogen degradation by more than 120%, 10 nM EGF increased glycogenolysis by less than 20% in hepatocytes incubated in glucose-free medium. Both glucagon and adrenaline increased phosphorylase a activity by more than 130%; EGF increased this activity by about 30%. Under basal conditions, 65% of the glucosyl residues were released as free glucose and about 30% ended up as C3 molecules (lactate and pyruvate). Both glucagon and adrenaline decreased the proportion of glucosyl units that rendered glycolysis end-products (to 2% for glucagon and 6% for adrenaline) and increased the proportion that ended up as free glucose (to 94% and 88% of the glucosyl residues for glucagon and adrenaline respectively). EGF increased the production of both free glucose and lactate+pyruvate, but the proportion of glucosyl residues that ended up as free glucose or glycolysis end-products was unchanged. In glycogen-depleted hepatocytes incubated in the presence of 25 mM glucose, EGF affected neither glycogen deposition nor glycolysis. EGF increased cytosolic free Ca2+, and neomycin decreased both the Ca2+ signal and the glycogenolytic effect. In conclusion, our results indicate that the effect of EGF on glycolysis is secondary to the Ca(2+)-mediated stimulation of glycogenolysis in rat hepatocyte suspensions.

Sign in / Sign up

Export Citation Format

Share Document