scholarly journals Insulin stimulates synthesis of soluble proteins in isolated rat hepatocytes

1980 ◽  
Vol 190 (3) ◽  
pp. 615-619 ◽  
Author(s):  
R L Clark ◽  
R J Hansen
Keyword(s):  
Protein Synthesis ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Cellular Protein ◽  
Soluble Proteins ◽  
Leucine Incorporation ◽  
Isolated Rat Hepatocytes ◽  
Hepatic Protein Synthesis ◽  
Isolated Rat ◽  
Stimulation Of

The incorporation of [3H]leucine into soluble cellular protein was measured in isolated hepatocytes at extracellular leucine concentrations ranging from 0.15 to 20.0 mM. Insulin caused a 12—15% stimulation of [3H]leucine incorporation in the presence of high extracellular leucine concentrations. It is concluded that insulin causes a small but significant increase in the rate of hepatic protein synthesis.

scholarly journals Homocysteine enhances the inhibitory effect of extracellular adenosine on the synthesis of proteins in isolated rat hepatocytes

1995 ◽  
Vol 310 (3) ◽  
pp. 893-896 ◽  
Author(s):  
S Tinton ◽  
P Buc-Calderon
Keyword(s):  
Protein Synthesis ◽  
Kinase Inhibitor ◽  
Adenine Nucleotides ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Adenosine Kinase ◽  
Isolated Rat Hepatocytes ◽  
Extracellular Adenosine ◽  
Inhibition Of Protein Synthesis ◽  
Isolated Rat

Previous work has shown that extracellular adenosine inhibits the incorporation of radiolabelled leucine into proteins in isolated rat hepatocytes [Tinton, Lefebvre, Cousin and Buc Calderon (1993) Biochim. Biophys. Acta 1176, 1-6]. In this study, we investigated whether its metabolism into adenine nucleotides, inosine or S-adenosylhomocysteine (AdoHcy) is required to induce such an impairment. Incubation of isolated hepatocytes in the presence of adenosine at 0.5 or 1 mM reduces the synthesis of proteins by about 45% after 120 min of incubation. Such an inhibition occurred without cell lysis and was not modified by adding the adenosine kinase inhibitor 5-iodotubercidin (15 microM) or the adenosine deaminase inhibitor coformycin (0.1 microM). It is therefore unlikely that the anabolic and catabolic pathways of adenosine are involved in the inhibition of protein synthesis. Adenosine (1 mM) increased the level of AdoHcy and S-adenosylmethionine by 20- and 5-fold respectively after 60 min of incubation and reduced the methylation index. These events as well as the inhibition of protein synthesis were strongly enhanced in the presence of L-homocysteine (2 mM). It is therefore concluded that the metabolism of adenosine into AdoHcy, which is known to be a potent inhibitor of cellular methylation reactions, may play an important role in the control of translation.

scholarly journals Effect of calcium ions on ethanol oxidation and drug glucuronidation in isolated hepatocytes

1979 ◽  
Vol 184 (3) ◽  
pp. 709-711 ◽  
Author(s):  
B Andersson ◽  
D P Jones ◽  
S Orrenius
Keyword(s):  
Drug Metabolism ◽  
Calcium Ions ◽  
Ethanol Oxidation ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Physiological Concentration ◽  
Isolated Rat Hepatocytes ◽  
Similar Dependence ◽  
Isolated Rat ◽  
Stimulation Of

The effect of extracellular Ca2+ concentration on ethanol oxidation and drug metabolism was studied in isolated rat hepatocytes. Both ethanol oxidation and drug glucuronidation showed similar dependence upon Ca2+, which was a stimulation of activity as Ca2+ was increased to physiological concentration, and inhibition at higher concentration.

Effects of temperature on protein turnover in isolated rat skeletal muscle

1984 ◽  
Vol 246 (1) ◽  
pp. C125-C130 ◽  
Author(s):  
V. E. Baracos ◽  
E. J. Wilson ◽  
A. L. Goldberg
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Muscle Protein ◽  
Rat Hepatocytes ◽  
Isolated Rat Hepatocytes ◽  
Body Protein ◽  
Influence Of Temperature On ◽  
Net Protein ◽  
Isolated Rat ◽  
Stimulation Of

To understand the net loss of muscle protein during fever and the possible changes in body protein balance with hyperthermia, we investigated the influence of temperature on protein synthesis and degradation in rat skeletal muscles. In the incubated soleus, extensor digitorum longus, or diaphragm, net protein degradation increased by about 11%/degrees C between 33 and 42 degrees C. This loss of muscle protein resulted from an increase in protein degradation (172% between 33 and 42 degrees C). By contrast, protein synthesis increased by only 25% between 33 and 39 degrees C and fell markedly by 42 degrees C. Unlike muscle, in isolated rat hepatocytes, protein breakdown did not increase significantly between 36 and 39 degrees C. The stimulation of protein degradation between 36 and 39 degrees C was not reduced by leupeptin or Ep-475, which inhibit lysosomal thiol proteases and reduce net protein degradation in the incubated muscles. Prostaglandin E2 (PGE2) has been implicated in the accelerated muscle proteolysis during fever. However, PGE2 release by muscles was unchanged between 33 and 42 degrees C, and inhibition of PGE2 synthesis by indomethacin did not reduce the stimulation of proteolysis at 40 degrees C. This catabolic effect of increased temperature may contribute to the negative nitrogen balance during fever.

scholarly journals The mechanism by which adenosine decreases gluconeogenesis from lactate in isolated rat hepatocytes

1987 ◽  
Vol 246 (2) ◽  
pp. 449-454 ◽  
Author(s):  
A Lavoinne ◽  
H A Buc ◽  
S Claeyssens ◽  
M Pinosa ◽  
F Matray
Keyword(s):  
Ketone Body ◽  
Adenine Nucleotides ◽  
Rat Hepatocytes ◽  
Adenosine Kinase ◽  
Isolated Rat Hepatocytes ◽  
Adenosine Deaminase 2 ◽  
Body Production ◽  
Gluconeogenic Substrates ◽  
Isolated Rat ◽  
Stimulation Of

Incubation of hepatocytes from 24 h-starved rats in the presence of 0.5 mM-adenosine decreased gluconeogenesis from lactate, but not from alanine. The inhibition of gluconeogenesis was associated with a stimulation of ketone-body production and an inhibition of pyruvate oxidation. These metabolic changes were suppressed in the presence of iodotubercidin (an inhibitor of adenosine kinase), but were reinforced in the presence of deoxycoformycin (an inhibitor of adenosine deaminase); 2-chloroadenosine induced no change in gluconeogenesis from lactate. These data indicate that the inhibition of gluconeogenesis by adenosine probably results from its conversion into adenine nucleotides. In the presence of lactate or pyruvate, but not with alanine or asparagine, this conversion resulted in a decrease in the [ATP]/[ADP] ratio in both mitochondrial and cytosolic compartments. Adenosine decreased the Pi concentration with all gluconeogenic substrates.

scholarly journals Effect of adenosine and inosine on ureagenesis in hepatocytes

1987 ◽  
Vol 245 (2) ◽  
pp. 371-374 ◽  
Author(s):  
R Guinzberg P ◽  
I Laguna ◽  
A Zentella ◽  
R Guzman ◽  
E Piña
Keyword(s):  
Uric Acid ◽  
Rat Hepatocytes ◽  
Physiological Significance ◽  
Isolated Rat Hepatocytes ◽  
Dose Dependent ◽  
Isolated Rat ◽  
Stimulation Of

Adenosine and inosine produced a dose-dependent stimulation of ureagenesis in isolated rat hepatocytes. Hypoxanthine, xanthine and uric acid were without effect. Half-maximally effective concentrations were 0.08 microM for adenosine and 5 microM for inosine. Activation of ureagenesis by both nucleosides had the following characteristics: (a) it was observed with either glutamine or (NH4)2CO3, provided that glucose was present; (b) it was not detected when glucose was replaced by lactate plus oleate; (c) it was mutually antagonized by glucagon, but not by adrenaline; and (d) it was dependent on Ca2+. We suggest that the action of adenosine and inosine on ureagenesis might be of physiological significance.

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