scholarly journals Kupffer cell stimulation of alpha2-macroglobulin synthesis in rat hepatocytes and the role of glucocorticoid.

1987 ◽  
Vol 12 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Satoshi Kurokawa ◽  
Hiromi Ishibashi ◽  
Kazuhiro Hayashida ◽  
Yoshihiro Tsuchiya ◽  
Yasuhiko Hirata ◽  
...  
Keyword(s):  
Kupffer Cell ◽  
Rat Hepatocytes ◽  
Cell Stimulation ◽  
Stimulation Of

scholarly journals The Role of Collagen Structure in Mitogen Stimulation of ERK, Cyclin D1 Expression, and G1-S Progression in Rat Hepatocytes

2003 ◽  
Vol 278 (34) ◽  
pp. 31691-31700 ◽  
Author(s):  
John T. Fassett ◽  
Diane Tobolt ◽  
Christopher J. Nelsen ◽  
Jeffrey H. Albrecht ◽  
Linda K. Hansen
Keyword(s):  
Cyclin D1 ◽  
Rat Hepatocytes ◽  
Collagen Structure ◽  
Mitogen Stimulation ◽  
Stimulation Of

scholarly journals Physiological concentrations of 2-oxoglutarate regulate the activity of phosphoenolpyruvate carboxykinase in liver

1992 ◽  
Vol 285 (3) ◽  
pp. 767-771 ◽  
Author(s):  
M A Titheradge ◽  
R A Picking ◽  
R C Haynes
Keyword(s):  
Pyruvate Kinase ◽  
Rat Liver ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Rat Hepatocytes ◽  
Fasted State ◽  
Stimulation Of

2-Oxoglutarate was found to inhibit purified rat liver phosphoenolpyruvate carboxykinase when the assay was performed in the direction of either phosphoenolpyruvate or oxaloacetate synthesis. The inhibition was competitive with respect to oxaloacetate or phosphoenolpyruvate, the Ki values being 0.32 +/- 0.04 mM 0.63 +/- 0.19 mM respectively. 2-Oxoglutarate inhibited non-competitively when tested against GTP or Mn2+. The reported cytosolic concentrations of 2-oxoglutarate in rat hepatocytes are such that the enzyme is likely to be significantly inhibited under basal conditions. The cytosolic concentration of 2-oxoglutarate is known to fall precipitously under the influence of glucagon and other hormones that stimulate gluconeogenesis, and it is suggested that the hormone-induced decrease in 2-oxoglutarate content would alleviate the inhibition of phosphoenolpyruvate carboxykinase and stimulate flux from oxaloacetate to phosphoenolpyruvate. The implications of this finding to the rationalization of the role of pyruvate kinase in the stimulation of gluconeogenesis in the fasted state are discussed.

scholarly journals Regulation of type 3 deiodinase in rodent liver and adipose tissue during fasting

2020 ◽  
Vol 9 (6) ◽  
pp. 552-562
Author(s):  
Emmely M de Vries ◽  
Hermina C van Beeren ◽  
Albert C W A van Wijk ◽  
Andries Kalsbeek ◽  
Johannes A Romijn ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Thyroid Hormone ◽  
Mrna Expression ◽  
Constitutive Androstane Receptor ◽  
Mtor Inhibitors ◽  
Rat Hepatocytes ◽  
Primary Hepatocytes ◽  
Type 3 ◽  
Stimulation Of

Fasting induces profound changes in the hypothalamus-pituitary-thyroid axis and peripheral thyroid hormone (TH) metabolism, ultimately leading to lower serum thyroid hormone (TH) concentrations. In the present study, we aimed to investigate the regulation of type 3 deiodinase (D3) during fasting in two metabolic tissues: liver and white adipose tissue (WAT). To this end, we studied the effect of modulation of the mammalian target of rapamycin (mTOR) and hypoxia inducible factor 1α (HIF1α) on D3 expression in primary rat hepatocytes and in 3T3-L1 adipocytes. In addition, we studied the role of the constitutive androstane receptor (CAR) on liver TH metabolism using primary hepatocytes and CAR-/- mice. Twenty-four-hour fasting increased liver Dio3 expression in mice. Inhibition of mTOR using mTOR inhibitors markedly induced Dio3 mRNA expression in primary hepatocytes; this increase was accompanied by a small increase in D3 activity. Stimulation of these cells with a CAR agonist induced both Dio3 mRNA expression and activity. Fasting increased hepatic D3 expression in WT but not in CAR-/- mice. In WAT, Dio3 mRNA expression increased five-fold after 48-h fasting. Treatment of 3T3-L1 adipocytes with mTOR inhibitors induced Dio3 mRNA expression, whereas stimulation of these cells with cobalt chloride, a compound that mimics hypoxia and stabilizes HIF1α, did not induce Dio3 mRNA expression. In conclusion, our results indicate an important role of mTOR in the upregulation of D3 in WAT and liver during fasting. Furthermore, CAR plays a role in the fasting induced D3 increase in the liver.

scholarly journals Glucagon stimulation of hepatic Na+-pump activity and α-subunit phosphorylation in rat hepatocytes

1996 ◽  
Vol 313 (3) ◽  
pp. 983-989 ◽  
Author(s):  
Christopher J. LYNCH ◽  
Kenneth M. McCALL ◽  
Yuk-Chow NG ◽  
Stacy A. HAZEN
Keyword(s):  
Protein Kinase ◽  
Rat Kidney ◽  
Rat Hepatocytes ◽  
Transport Activity ◽  
Isolated Rat Hepatocytes ◽  
Α Subunit ◽  
Na Pump ◽  
Pump Activity ◽  
Stimulation Of

In this study the possible role of Na+ influx, arachidonate mediators and α-subunit phosphorylation in the stimulatory response of hepatic Na+/K+-ATPase to glucagon was examined. Glucagon stimulation of ouabain-sensitive 86Rb+ uptake in freshly isolated rat hepatocytes reached maximal levels in less than 1 min after hormone addition and was half-maximal (EC50) at a concentration of 2.4(±1.3)×10-10 M. Analysis of the K+-dependence of this response indicates an effect on the apparent Vmax. for K+ with no significant change in the apparent K0.5. Unlike monensin, glucagon stimulation of Na+/K+-ATPase-mediated transport activity was not associated with an increase in 22Na+ influx. This indicates that the stimulation of Na+/K+-ATPase by glucagon is not secondary to an increase in Na+ influx. A role for arachidonate mediators in this effect also appears unlikely because neither basal nor glucagon-stimulated ouabain-sensitive 86Rb+ uptake was significantly affected by supramaximal concentrations of cyclo-oxygenase, lipoxygenase, cytochrome P-450 or phospholipase A2 inhibitors. To study the possible role of protein kinase-mediated phosphorylation in the stimulation of ouabain-sensitive 86Rb+ uptake, hepatocytes were metabolically radiolabelled with [32P]Pi. Glucagon stimulated incorporation of 32P into a 95 kDa phosphoprotein that co-migrates with Na+/K+-ATPase α-subunit immunoreactivity in two-dimensional gel electrophoresis. The α-subunit could be immunoprecipitated from detergent-solubilized particulate fractions of hepatocytes using an anti-(rat kidney Na+/K+-ATPase) serum. When hepatocytes were metabolically radiolabelled with [32P]Pi, the immunoprecipitated α-subunit contained 32P. Glucagon increased the incorporation of 32P into the immunoprecipitated subunit by 197±21% (n = 6). Similar results were observed with a rabbit anti-peptide serum (‘anti-LEAVE’ serum) prepared against an amino acid sequence in the α-subunit. The EC50 for glucagon-stimulated phosphorylation of the α-subunit (1×10-10 M) was very close to that for glucagon stimulation of ouabain-sensitive 86Rb+ uptake. In conclusion, it appears that glucagon stimulation of hepatic Na+/K+-ATPase-mediated transport activity is not secondary to increases in Na+ influx or changes in the levels of an arachidonate mediator. The data provide support for the hypothesis that glucagon stimulation of Na+-pump activity in hepatocytes may be related to protein kinase-mediated changes in the phosphorylation state of the α-subunit.

scholarly journals The role of cytosolic Ca2+, protein kinase C, and protein kinase A in hormonal stimulation of phospholipase D in rat hepatocytes.

1994 ◽  
Vol 269 (2) ◽  
pp. 849-859
Author(s):  
L. Gustavsson ◽  
G. Moehren ◽  
M.E. Torres-Marquez ◽  
C. Benistant ◽  
R. Rubin ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Kinase A ◽  
Phospholipase D ◽  
Rat Hepatocytes ◽  
Hormonal Stimulation ◽  
Kinase C ◽  
Kinase A ◽  
Stimulation Of

Stimulation of Ca(2+)-dependent exocytosis of the sperm acrosome by cAMP acting downstream of phospholipase A2

Reproduction ◽  
2000 ◽  
pp. 57-68 ◽  
Author(s):  
J Garde ◽  
ER Roldan
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Phosphodiesterase Inhibitors ◽  
Dibutyryl Camp ◽  
Camp Phosphodiesterase ◽  
Ram Sperm ◽  
Camp Formation ◽  
Stimulation Of

Spermatozoa undergo exocytosis in response to agonists that induce Ca2+ influx and, in turn, activation of phosphoinositidase C, phospholipase C, phospholipase A2, and cAMP formation. Since the role of cAMP downstream of Ca2+ influx is unknown, this study investigated whether cAMP modulates phospholipase C or phospholipase A2 using a ram sperm model stimulated with A23187 and Ca2+. Exposure to dibutyryl-cAMP, phosphodiesterase inhibitors or forskolin resulted in enhancement of exocytosis. However, the effect was not due to stimulation of phospholipase C or phospholipase A2: in spermatozoa prelabelled with [3H]palmitic acid or [14C]arachidonic acid, these reagents did not enhance [3H]diacylglycerol formation or [14C]arachidonic acid release. Spermatozoa were treated with the phospholipase A2 inhibitor aristolochic acid, and dibutyryl-cAMP to test whether cAMP acts downstream of phospholipase A2. Under these conditions, exocytosis did not occur in response to A23187 and Ca2+. However, inclusion of dibutyryl-cAMP and the phospholipase A2 metabolite lysophosphatidylcholine did result in exocytosis (at an extent similar to that seen when cells were treated with A23187/Ca2+ and without the inhibitor). Inclusion of lysophosphatidylcholine alone, without dibutyryl-cAMP, enhanced exocytosis to a lesser extent, demonstrating that cAMP requires a phospholipase A2 metabolite to stimulate the final stages of exocytosis. These results indicate that cAMP may act downstream of phospholipase A2, exerting a regulatory role in the exocytosis triggered by physiological agonists.

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