scholarly journals The accumulation of aspartate in the presence of ethanol in rat liver

1975 ◽  
Vol 150 (1) ◽  
pp. 41-45 ◽  
Author(s):  
M Stubbs ◽  
H A Krebs
Keyword(s):  
Rat Liver ◽  
Aspartate Aminotransferase ◽  
Isolated Hepatocytes ◽  
Perfused Liver ◽  
Isolated Cells ◽  
Isolated Rat Liver ◽  
Ammonium Lactate ◽  
Mitochondrial Aspartate Aminotransferase ◽  
Isolated Rat ◽  
Dehydrogenation Of Ethanol

1. Isolated hepatocytes were used to establish the reasons for the accumulation of aspartate, previously observed when the isolated rat liver was perfused with ethanol in the presence of alanine or ammonium lactate. 2. The isolated cells did not form aspartate when incubated with alanine and ethanol, but much aspartate was formed on incubation with ammonium lactate and ethanol. 3. Urea was the main nitrogenous product on incubation with alanine, in contrast with the perfused liver, where major quantities of NH4+ are also formed. When the formation of urea was nullified by the addition of urease, alanine plus ethanol caused aspartate formation, indicating that aspartate formation depends on the presence of critical concentrations of NH4+. 4. The accumulated aspartate was present in the cytosol. Ethanol halved the content of 2-oxoglutarate in the cytosol and more than trebled that of glutamate in the mitochondria. 5. The findings support the assumption that 2-oxoglutarate formed by the mitochondrial aspartate aminotransferase is not translocated to the cytosol in the presence of ethanol and NH4+, because it is rapidly converted into glutamate, the dehydrogenation of ethanol providing the required NADH. Aspartate, however, is translocated to the cytosol and accumulates there because of the lack of stoicheiometric amounts of oxoglutarate.

scholarly journals The effects L-leucine on the synthesis of urea, glutamate and glutamine by isolated rat liver cells

1975 ◽  
Vol 146 (2) ◽  
pp. 457-464 ◽  
Author(s):  
J M Mourão ◽  
J D McGivan ◽  
J B Chappell
Keyword(s):  
Amino Acids ◽  
Nitrogen Source ◽  
Glutamate Dehydrogenase ◽  
Rat Liver ◽  
Liver Cells ◽  
Carbamoyl Phosphate ◽  
Isolated Cells ◽  
Isolated Rat Liver ◽  
Rat Liver Cells ◽  
Isolated Rat

With either alanine or a mixture of 15 different amino acids as nitrogen source, the addition of L-leucine inhibited the synthesis of urea by isolated rat liver cells. With alanine present leucine promoted the production of glutamate and glutamine. Comparison of effects of leucine on soluble glutamate dehydrogenase, mitochondria and isolated cells supports the postulate that leucine exerts its effect through activation of glutamate dehydrogenase. It is suggested that this latter enzyme may not be as important for the production of NH3 for carbamoyl phosphate synthesis as has been considered hitherto.

Perfusion of rat’s liver with blood: transmitter overflows and gluconeogenesis

1970 ◽  
Vol 174 (1037) ◽  
pp. 503-515 ◽  
Keyword(s):  
Guinea Pig ◽  
Rat Liver ◽  
Nerve Stimulation ◽  
Perfused Liver ◽  
Methyl Transferase ◽  
Isolated Rat Liver ◽  
Lactate Utilization ◽  
Transmitter Uptake ◽  
Sympathetic Transmitter ◽  
Isolated Rat

A simplified apparatus for the perfusion of the isolated rat liver is described. The operative technique has been developed so as to avoid any interruption in the blood supply to the liver. By the generally accepted criteria of viability the liver remains almost normal for up to 4 h. Perfusion with oxygenated blood through both the hepatic artery and portal vein confers no special advantages over portal perfusion alone, as judged by lactate utilization. No overflows of sympathetic transmitter could be detected from the perfused liver of the rat after nerve stimulation unless catechol- O -methyl transferase inhibitors were present; even in the presence of phenoxybenzamine (to block transmitter uptake by nerve endings) overflows were small. Larger transmitter overflows were obtained from the perfused liver of guinea-pig. Nerve stimulation caused a transient increase in the rate of gluconeogenesis by the rat liver; the maximum response, an increase of 60 %, occurred after 5 min stimulation at a frequency of 10 Hz.

scholarly journals Glucagon and vasopressin interactions on Ca2+ movements in isolated hepatocytes

1986 ◽  
Vol 237 (3) ◽  
pp. 675-683 ◽  
Author(s):  
L Combettes ◽  
B Berthon ◽  
A Binet ◽  
M Claret
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Isolated Hepatocytes ◽  
Liver Cells ◽  
Isolated Rat Liver ◽  
Low Concentration ◽  
Fast Phase ◽  
Rat Liver Cells ◽  
Subsequent Addition ◽  
Isolated Rat

The effects of glucagon and vasopressin, singly or together, on cytosolic free Ca2+ concentration [(Ca2+]i) and on the 45Ca2+ efflux were studied in isolated rat liver cells. In the presence of 1 mM external Ca2+, glucagon and vasopressin added singly induced sustained increases in [Ca2+]i. The rate of the initial fast phase of the [Ca2+]i increase and the magnitude of the final plateau were dependent on the concentrations (50 pm-0.1 microM) of glucagon and vasopressin. Preincubating the cells with a low concentration of glucagon (0.1 nM) for 2 min markedly accelerated the fast phase and elevated the plateau of the [Ca2+]i increase caused by vasopressin. In the absence of external free Ca2+, glucagon and vasopressin transiently increased [Ca2+]i and stimulated the 45Ca2+ efflux from the cells, indicating mobilization of Ca2+ from internal store(s). Preincubating the cells with 0.1 nM-glucagon accelerated the rate of the fast phase of the [Ca2+]i rise caused by the subsequent addition of vasopressin. However, unlike what was observed in the presence of 1 mM-Ca2+, glucagon no longer enhanced the maximal [Ca2+]i response to vasopressin. In the absence of external free Ca2+, higher concentrations (1 nM-0.1 microM) of glucagon, which initiated larger increases in [Ca2+]i, drastically decreased the subsequent Ca2+ response to vasopressin (10 nM). At these concentrations, glucagon also decreased the vasopressin-stimulated 45Ca2+ efflux from the cells. It is suggested that, in the liver, glucagon accelerates the fast phase and elevates the plateau of the vasopressin-mediated [Ca2+]i increase respectively by releasing Ca2+ from the same internal store as that permeabilized by vasopressin, probably the endoplasmic reticulum, and potentiating the influx of extracellular Ca2+ caused by this hormone.

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