Characterization of glucagon and catecholamine effects on isolated sheep hepatocytes

1988 ◽  
Vol 255 (4) ◽  
pp. R539-R546
Author(s):  
C. Morand ◽  
C. Yacoub ◽  
C. Remesy ◽  
C. Demigne
Keyword(s):  
Rat Liver ◽  
Glycogen Phosphorylase ◽  
Plasma Membranes ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Cyclic Monophosphate ◽  
Sheep Liver ◽  
Beta Agonists ◽  
Rat Liver Cells

The purpose of this study was to characterize the glycogenolytic response to catecholamines and glucagon in isolated sheep hepatocytes. In this species, epinephrine appeared to exert its action on hepatic glycogenolysis by altering the cytosolic concentrations of both adenosine 3',5'-cyclic monophosphate (cAMP) and Ca2+. In contrast to results obtained in rat hepatocytes, glucagon failed to induce a rise in free cytosolic Ca2+ in sheep liver. Experiments on isolated hepatocytes or on liver plasma membranes showed that in sheep, glucagon was more efficient than epinephrine in promoting the production of cAMP. In the presence of glucagon or epinephrine, the activation of the glycogen phosphorylase a always appeared greater in sheep than in rat liver cells, whereas the variations in cellular cAMP were quite limited in sheep. The alpha 1- and beta-agonists (phenylephrine and isoproterenol) were alone as efficient as epinephrine in promoting phosphorylase a activation in sheep hepatocytes. All these results indicate the existence in sheep liver of a glycogen phosphorylase highly responsive to hormones.

scholarly journals Characterization of the liver P2-purinoceptor involved in the activation of glycogen phosphorylase

1986 ◽  
Vol 240 (2) ◽  
pp. 367-371 ◽  
Author(s):  
S Keppens ◽  
H De Wulf
Keyword(s):  
Binding Sites ◽  
Glycogen Phosphorylase ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Rank Order ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Isolated Rat Hepatocytes ◽  
P2 Purinoceptors

Evidence has been presented for the existence in rat liver of P2-purinoceptors which are involved in the control of glycogenolysis. Isolated rat hepatocytes and purified liver plasma membranes have been used to study the binding of the ATP analogue adenosine 5′-[alpha- [35S]thio]triphosphate (ATP alpha [35S]) to these postulated P2-purinoceptors. The nucleotide analogue behaves as a full agonist for the activation of glycogen phosphorylase in isolated hepatocytes, 0.3 microM being required for half-maximal activation. Specific binding of ATP alpha [35S] to hepatocytes and plasma membranes occurs within 1 min and is essentially reversible. The analysis of the dose-dependency at equilibrium indicates the presence of binding sites with Kd of 0.23 microM with hepatocytes and Kd of 0.11 microM with plasma membranes. The relative affinities of 10 nucleotide analogues were deduced from competition experiments for ATP alpha [35S] binding to hepatocytes, and these correlated highly with their biological activity (activation of glycogen phosphorylase in hepatocytes). For all the agonists, binding occurs in the same concentration range as the biological effect. These data clearly suggest that the detected binding sites correspond to the physiological P2-purinoceptors involved in the regulation of liver glycogenolysis. The rank order of potency of some ATP analogues suggests that liver possesses the P2Y-subclass of P2-purinoceptors.

scholarly journals Effects of taurolithocholate, a Ca2+-mobilizing agent, on cell Ca2+ in rat hepatocytes, human platelets and neuroblastoma NG108-15 cell line

1991 ◽  
Vol 273 (1) ◽  
pp. 153-160 ◽  
Author(s):  
J F Coquil ◽  
B Berthon ◽  
N Chomiki ◽  
L Combettes ◽  
P Jourdon ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Bile Acid ◽  
Cell Line ◽  
Rat Liver ◽  
Neuronal Cell ◽  
Rat Hepatocytes ◽  
Cell Types ◽  
Liver Cells ◽  
Human Platelets ◽  
Rat Liver Cells

The monohydroxy bile acid taurolithocholate permeabilizes the endoplasmic reticulum to Ca2+ in rat liver cells. To assess whether this action on the endoplasmic reticulum was restricted to this tissue, the effects of bile acid were investigated in two cell types quite unrelated to rat hepatocyte, namely human platelets and neuronal NG108-15 cell line. The results showed that taurolithocholate (3-100 microM) had no effect on free cytosolic [Ca2+] in human platelets and NG108-15 cells. whereas it increased it from 180 to 520 nM in rat hepatocytes. In contrast, in cells permeabilized by saponin, taurolithocholate initiated a profound release of the stored Ca2+ from the internal Ca2+ pools in the three cell types. The bile acid released 90% of the Ca2+ pools, with rate constants of about 5 min-1 and half-maximal effects at 15-30 microM. The results also showed that, in contrast with liver cells, which displayed an influx of [14C]taurolithocholate of 2 nmol/min per mg, human platelets and the neuronal cell line appeared to be resistant to [14C]taurolithocholate uptake. The influx measured in these latter cells was about 100-fold lower than in rat liver cells. Taken together, these data suggest that human platelets and NG108-15 cells do not possess the transport system for concentrating monohydroxy bile acids into cells. However, they show that human platelets and neuronal NG108-15 possess, in common with liver cells, the intracellular system responsible for taurolithocholate-mediated Ca2+ release from internal stores.

scholarly journals Isolation and partial characterization of a fatty acid binding protein in rat liver plasma membranes.

1985 ◽  
Vol 82 (1) ◽  
pp. 4-8 ◽  
Author(s):  
W. Stremmel ◽  
G. Strohmeyer ◽  
F. Borchard ◽  
S. Kochwa ◽  
P. D. Berk
Keyword(s):  
Fatty Acid ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Fatty Acid Binding Protein ◽  
Binding Protein ◽  
Partial Characterization ◽  
Fatty Acid Binding ◽  
Acid Binding Protein ◽  
Rat Liver Plasma Membranes

scholarly journals Subcellular localization of sterol carrier protein-2 in rat hepatocytes: its primary localization to peroxisomes.

1989 ◽  
Vol 108 (4) ◽  
pp. 1353-1361 ◽  
Author(s):  
G A Keller ◽  
T J Scallen ◽  
D Clarke ◽  
P A Maher ◽  
S K Krisans ◽  
...  
Keyword(s):  
Subcellular Localization ◽  
Rat Liver ◽  
Polyclonal Antibodies ◽  
Rat Hepatocytes ◽  
Carrier Protein ◽  
Sterol Carrier Protein ◽  
Rat Liver Cells ◽  
Ultrathin Frozen Sections ◽  
Sterol Carrier Protein 2

Sterol carrier protein-2 (SCP-2) is a nonenzymatic protein of 13.5 kD which has been shown in in vitro experiments to be required for several stages in cholesterol utilization and biosynthesis. The subcellular localization of SCP-2 has not been definitively established. Using affinity-purified rabbit polyclonal antibodies against electrophoretically pure SCP-2 from rat liver, we demonstrate by immunoelectron microscopic labeling of ultrathin frozen sections of rat liver that the largest concentration of SCP-2 is inside peroxisomes. In addition the immunolabeling indicates that there are significant concentrations of SCP-2 inside mitochondria, and associated with the endoplasmic reticulum and the cytosol, but not inside the Golgi apparatus, lysosomes, or the nucleus. These results were confirmed by immunoblotting experiments with proteins from purified subcellular fractions of the rat liver cells carried out with the anti-SCP-2 antibodies. The large concentration of SCP-2 inside peroxisomes strongly supports the proposal that peroxisomes are critical sites of cholesterol utilization and biosynthesis. The presence of SCP-2 inside peroxisomes and mitochondria raises questions about the mechanisms involved in the differential targeting of SCP-2 to these organelles.

scholarly journals Polyribosomes in isolated liver cells. Preparative procedures, effects of incubation and correlation with protein synthesis

1980 ◽  
Vol 186 (1) ◽  
pp. 35-45 ◽  
Author(s):  
A J Dickson ◽  
C I Pogson
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Isolated Hepatocytes ◽  
Liver Cells ◽  
Liver Protein ◽  
Isolated Cells ◽  
Isolated Liver Cells ◽  
Rat Liver Cells ◽  
Isolated Liver

Methods have been derived which permit the isolation of undergraded polyribosomes from isolated rat liver cells. Under the conditions used the polyribosome profile of hepatocytes immediately after isolation was essentially identical with that from intact liver. However, during incubation of cells in complex physiological media there was a progressive dissociation of polyribosomes. The addition of a variety of factors that produce reaggregation of polyribosomes in rat liver in vivo did not prevent dissociation during cell incubations. Although large polyribosomes were lost most rapidly, the albumin-synthesizing capacity of isolated cells was not selectively lost when compared with total protein synthesis. The significance of these results for the use of isolated hepatocytes in the study of liver protein synthesis is discussed.

Lectin-binding patterns on the plasma membranes of dissociated rat liver cells

1984 ◽  
Vol 80 (5) ◽  
pp. 415-420 ◽  
Author(s):  
H. Kawakami ◽  
H. Hirano
Keyword(s):  
Rat Liver ◽  
Plasma Membranes ◽  
Lectin Binding ◽  
Liver Cells ◽  
Rat Liver Cells

The chemistry and biology of 7H-dibenzo[c,g]carbazole: synthesis and characterization of selected derivatives, metabolism in rat liver preparations and mutagenesis mediated by cultured rat hepatocytes

1989 ◽  
Vol 10 (3) ◽  
pp. 419-427 ◽  
Author(s):  
David B. Stong ◽  
Robert T. Christian ◽  
Koka Jayasimhulu ◽  
R.Marshall Wilson ◽  
David Warshawsky
Keyword(s):  
Rat Liver ◽  
Rat Hepatocytes ◽  
Synthesis And Characterization ◽  
Cultured Rat Hepatocytes
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