scholarly journals Potentiation by ammonia of the metabolic effects of pent-4-enoate in isolated rat hepatocytes

1984 ◽  
Vol 224 (1) ◽  
pp. 263-267 ◽  
Author(s):  
F X Coudé ◽  
G Grimber ◽  
P Parvy ◽  
D Rabier ◽  
J Bardet
Keyword(s):  
Cellular Metabolism ◽  
Rat Hepatocytes ◽  
Metabolic Effects ◽  
Maximum Effect ◽  
Half Maximum ◽  
Isolated Rat Hepatocytes ◽  
Glucose Synthesis ◽  
Beta Hydroxybutyrate ◽  
Isolated Rat ◽  
Pyruvate Ratio

The metabolic effects of pent-4-enoate were studied in isolated rat hepatocytes; 1 mM-pent-4-enoate did not significantly inhibit gluconeogenesis from lactate, alanine and glycerol, but significantly decreased glucose synthesis from pyruvate. The addition of 1 mM-NH4Cl led to a drastic inhibition of glucose synthesis from all these substrates. In hepatocytes incubated with 10 mM-alanine and 1 mM-oleate, pent-4-enoate at 0.05-1 mM slightly inhibited glucose synthesis and ketogenesis. The addition of ammonia resulted in a dramatic potentiation of the metabolic effects of pent-4-enoate. Half-maximum effect of ammonia was observed at 0.2 mM concentration. Concomitant cellular concentrations of ATP and acetyl-CoA were also decreased by the addition of ammonia, as were lactate/pyruvate ratio and beta-hydroxybutyrate/acetoacetate ratio. These data suggest that ammonia seriously interferes with the cellular metabolism of pent-4-enoate and leads to a dramatic potentiation of its effects.

scholarly journals Microcystin-LR induced an inhibition of protein synthesis in isolated rat hepatocytes

1995 ◽  
Vol 306 (3) ◽  
pp. 693-696 ◽  
Author(s):  
S Claeyssens ◽  
A Francois ◽  
A Chedeville ◽  
A Lavoinne
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Rat Hepatocytes ◽  
Mitochondrial Fraction ◽  
Maximum Effect ◽  
Isolated Rat Hepatocytes ◽  
Phosphatase Inhibitors ◽  
Protein Phosphatase Inhibitors ◽  
Phosphatase Activation ◽  
Isolated Rat

The effect of microcystin-LR, an inhibitor of protein phosphatases PP1 and PP2A, was studied on protein synthesis by measuring the incorporation of labelled amino acid into protein in isolated rat hepatocytes. Microcystin-LR inhibited protein synthesis in the first minutes of the incubation period, and half-maximum effect was obtained at about 60 nM. Such an inhibition was also observed in the presence of different protein phosphatase inhibitors, i.e. okadaic acid, calyculin A and microcystin-RR. This effect was observed in whole hepatocytes, in the supernatant of the post-mitochondrial fraction and in the microsomal fraction. It was independent of a substrate supply and of the labelled amino acid used. Furthermore, this inhibition preceded the previously reported glucose-6-phosphatase activation induced by microcystin-LR [Claeyssens, Chédeville and Lavoinne (1993) FEBS Lett. 315, 7-10].

Effects of chronic uraemia on the formation of glucose and urea plus ammonia from l-alanine, l-glutamine and l-serine in isolated rat hepatocytes

1986 ◽  
Vol 70 (6) ◽  
pp. 627-634 ◽  
Author(s):  
Rita A. Klim ◽  
Marta Albajar ◽  
Reginald Hems ◽  
Dermot H. Williamson
Keyword(s):  
Glucose Production ◽  
Rat Hepatocytes ◽  
Nitrogen Release ◽  
Isolated Rat Hepatocytes ◽  
Metabolic Intermediates ◽  
Chronic Uraemia ◽  
Serine Dehydratase ◽  
Glucose Synthesis ◽  
Lactate And Pyruvate ◽  
Isolated Rat

1. The effects of chronic uraemia on glucose production and nitrogen release (urea plus ammonia formation) from alanine, glutamine or serine in isolated rat hepatocytes were studied. 2. Uraemia increased the rate of formation of urea plus ammonia from all three amino acids by 38-93% when they were present at a final concentration of 10 mmol/l. At lower concentrations (2 mmol/l) the rate of nitrogen release was not significantly increased. 3. Hepatocytes from normal rats whose food intake had been restricted to the level of that of uraemic rats did not show the increased rates of nitrogen release. 4. The increased rates of nitrogen release with hepatocytes from uraemic rats were not accompanied by increased rates of glucose synthesis. Instead, accumulation of metabolic intermediates occurred: lactate and pyruvate (alanine or serine as substrates) and glutamate (glutamine as substrate). 5. Livers of uraemic rats had increased activities of glutarninase (30%) and serine dehydratase (100%). 6. Hepatocytes from normal rats treated with phlorhizin to increase the plasma glucagon/insulin ratio behaved in a similar manner to hepatocytes from uraemic rats. They had increased serine dehydratase activity, and increased rates of utilization of serine or glutamine. 7. The possible implications of these findings for human uraemia are discussed.

scholarly journals Metabolic Effects of Glibenclamide in Isolated Rat Hepatocytes in the Absence of Extracellular Ca2+

1995 ◽  
Vol 69 (2) ◽  
pp. 173-176
Author(s):  
Takahide Nomura ◽  
Masatsugu Ohtsuki ◽  
Toshiko Watanabe ◽  
Seiko Hasegawa ◽  
Shigeru Matsui ◽  
...  
Keyword(s):  
Rat Hepatocytes ◽  
Metabolic Effects ◽  
Isolated Rat Hepatocytes ◽  
Isolated Rat

scholarly journals Effects of phorbol esters on α1-adrenergic-mediated and glucagon-mediated actions in isolated rat hepatocytes

1985 ◽  
Vol 228 (1) ◽  
pp. 277-280 ◽  
Author(s):  
J A García-Sáinz ◽  
F Mendlovic ◽  
M A Martínez-Olmedo
Keyword(s):  
Cyclic Amp ◽  
Dose Response ◽  
Response Curve ◽  
Phorbol Esters ◽  
Rat Hepatocytes ◽  
Metabolic Effects ◽  
Isolated Rat Hepatocytes ◽  
The Right ◽  
Isolated Rat ◽  
Stimulation Of

Phorbol 12-myristate 13-acetate (PMA) inhibited the stimulation of ureogenesis produced by adrenaline, but produced a minimal displacement to the right of the dose-response curve for glucagon. However, PMA diminished the accumulation of cyclic AMP induced by glucagon. Dissociation between the cyclic AMP concentrations and the metabolic effects induced by glucagon is evidenced in the presence of phorbol esters.

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