scholarly journals Differential effects of tryptophan on glucose synthesis in rats and guinea pigs

1978 ◽  
Vol 176 (3) ◽  
pp. 817-825 ◽  
Author(s):  
S A Smith ◽  
K R F Elliott ◽  
C I Pogson
Keyword(s):  
Rat Liver ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glucose Production ◽  
Rat Hepatocytes ◽  
Liver Cells ◽  
Isolated Rat Hepatocytes ◽  
Rat Liver Cells ◽  
Glucose Output ◽  
Isolated Rat

1. Tryptophan inhibition of gluconeogenesis in isolated rat liver cells is characterized by a 20 min lag period before linear rates of glucose output are attained. 2. Half-maximal inhibition of gluconeogenesis in isolated rat hepatocytes is produced by approx. 0.1 mM-tryptophan. 3. Tryptophan inhibits gluconeogenesis from all substrates giving rise to oxaloacetate, but stimulates glycerol-fuelled glucose production. 4. Gluconeogenesis in guinea-pig hepatocytes is insensitive to tryptophan. 5. Changes in metabolite concentrations in rat liver cells are consistent with a locus of inhibition at the step catalysed by phosphoenolpyruvate carboxykinase. 6. Inhibition of gluconeogenesis persists in cells from rats pretreated with tryptophan in vivo. 7. Tryptophan has no effect on urea production from alanine, but decreases [1-14C]palmitate oxidation to 14CO2 and is associated with an increased [hydroxybutyrate]/[acetoacetate] ratio. 8. These results are discussed with reference to the control of gluconeogenesis in various species.

Antiketogenic effect of glucose per se in vivo in man and in vitro in isolated rat liver cells

Metabolism ◽  
1986 ◽  
Vol 35 (7) ◽  
pp. 608-613 ◽  
Author(s):  
J.P. Riou ◽  
M. Beylot ◽  
M. Laville ◽  
L. De Parscau ◽  
J. Delinger ◽  
...  
Keyword(s):  
Rat Liver ◽  
Liver Cells ◽  
Isolated Rat Liver ◽  
Rat Liver Cells ◽  
Per Se ◽  
Effect Of Glucose ◽  
Isolated Rat

scholarly journals Calcium rather than cyclic AMP is an intracellular messenger of parathyroid hormone action on glycogen metabolism in isolated rat hepatocytes

1989 ◽  
Vol 258 (3) ◽  
pp. 889-894 ◽  
Author(s):  
T Mine ◽  
I Kojima ◽  
E Ogata
Keyword(s):  
Parathyroid Hormone ◽  
Cyclic Amp ◽  
Glucose Production ◽  
Rat Hepatocytes ◽  
Free Calcium ◽  
Dependent Manner ◽  
Isolated Rat Hepatocytes ◽  
Glucose Output ◽  
Dose Dependent ◽  
Isolated Rat

The synthetic 1-34 fragment of human parathyroid hormone (1-34hPTH) stimulated glucose production in isolated rat hepatocytes. The effect of 1-34hPTH was dose-dependent and 10(10) M-1-34 hPTH elicited the maximum glucose output, which was approx. 80% of that by glucagon. Although 1-34hPTH induced a small increase in cyclic AMP production at concentrations higher than 10(-9) M, 10(-10) M-1-34hPTH induced the maximum glucose output without significant elevation of cyclic AMP. This is in contrast to the action of forskolin, which increased glucose output to the same extent as 10(-10) M-1-34hPTH by causing a 2-fold elevation of cyclic AMP. In addition to increasing cyclic AMP, 1-34hPTH caused an increase in cytoplasmic free calcium concentration ([Ca2+]c). When the effect of 1-34hPTH on [Ca2+]c was studied in aequorin-loaded cells, low concentrations of 1-34hPTH increased [Ca2+]c: the 1-34hPTH effect on [Ca2+]c was detected at as low as 10(-12) M and increased in a dose-dependent manner. 1-34hPTH increased [Ca2+]c even in the presence of 1 microM extracellular calcium, suggesting that PTH mobilizes calcium from an intracellular pool. In line with these observations, 1-34hPTH increased the production of inositol trisphosphate. These results suggest that: (1) PTH activates both cyclic AMP and calcium messenger systems and (2) PTH stimulates glycogenolysis mainly via the calcium messenger system.

Vasopressin promotes the metabolism of near-physiological concentration of glutamine in isolated rat liver cells

1984 ◽  
Vol 4 (2) ◽  
pp. 171-176 ◽  
Author(s):  
Guy Martin ◽  
Gabriel Baverel
Keyword(s):  
Rat Liver ◽  
Liver Cells ◽  
Hepatic Gluconeogenesis ◽  
Physiological Concentration ◽  
Isolated Rat Liver ◽  
Rat Liver Cells ◽  
Isolated Rat

In isolated rat liver cells, vasopressin, like glucagon, promotes the metabolism of glutamine used at nearphysiological concentration (1 mM). These findings indicate that, in vivo, both hormones might participate in the control of hepatic gluconeogenesis and ureogenesis from glutamine.

scholarly journals Glutathione analogues as novel inhibitors of rat and human glutathione S-transferase isoenzymes, as well as of glutathione conjugation in isolated rat hepatocytes and in the rat in vivo

1995 ◽  
Vol 308 (1) ◽  
pp. 283-290 ◽  
Author(s):  
S Ouwerkerk-Mahadevan ◽  
J H van Boom ◽  
M C Dreef-Tromp ◽  
J H T M Ploemen ◽  
D J Meyer ◽  
...  
Keyword(s):  
Ethyl Ester ◽  
Rat Liver ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Glutathione S Transferase ◽  
Isolated Rat Hepatocytes ◽  
Glutathione S Transferases ◽  
Gamma S ◽  
Isolated Rat

Inhibitors of rat and human Alpha- and Mu-class glutathione S-transferases that effectively inhibit the glutathione (GSH) conjugation of bromosulphophthalein in the rat liver cytosolic fraction, isolated rat hepatocytes and in the rat liver in vivo have been developed. The GSH analogue (R)-5-carboxy-2-gamma-(S)-glutamylamino-N-hexylpentamide [Adang, Brussee, van der Gen and Mulder (1991) J. Biol. Chem. 266, 830-836] was used as the lead compound. To obtain more potent inhibitors, it was modified by replacement of the N-hexyl moiety by N-2-heptyl and by esterification of the 5-carboxy group with ethyl and dodecyl groups. In isolated hepatocytes, the branched N-2-heptyl derivatives were stronger inhibitors of GSH conjugation of bromosulphophthalein than the N-hexyl derivatives. The ethyl ester compounds were more efficient than the corresponding unesterified derivatives. The dodecyl ester of the N-2-heptyl analogue was the most effective inhibitor in isolated hepatocytes, but was relatively toxic in vivo. However, the corresponding ethyl ester was a potent in vivo inhibitor: GSH conjugation of bromosulphophthalein (as assessed by biliary excretion of the conjugate) was decreased by 70% after administration of a dose of 200 mumol/kg. The isoenzyme specificity of the inhibitors towards purified rat and human glutathione S-transferases was also examined. The unesterified compounds were more potent than the esterified analogues, and inhibited Alpha- and Mu-class isoenzymes of both rat and human glutathione S-transferase (Ki range 1-40 microM). Other GSH-dependent enzymes, i.e. GSH peroxidase, GSH reductase and gamma-glutamyltranspeptide, were not inhibited. Thus (R)-5-ethyloxycarbonyl-2-gamma-(S)-glutamylamino-N-2-hept ylpentamide, the in vivo inhibitor of GSH conjugation, may be useful in helping to assess the role of the Alpha and Mu classes of glutathione S-transferases in cellular biochemistry, physiology and pathology.

scholarly journals Hydroxypyruvate as a gluconeogenic substrate in rat hepatocytes*

1975 ◽  
Vol 146 (1) ◽  
pp. 277-279 ◽  
Author(s):  
D H Williamson ◽  
E V Ellington
Keyword(s):  
Rat Liver ◽  
Rat Hepatocytes ◽  
Liver Cells ◽  
Isolated Rat Liver ◽  
Rat Liver Cells ◽  
Gluconeogenic Substrate ◽  
Isolated Rat ◽  
Reducing Equivalents

At concentrations of 2mM and above hydroxypyruvate produced no glucose with isolated rat liver cells, although it was rapidly utilized. At a lower concentration of hydroxypyruvate or in the presence of substrates which generate reducing equivalents (ethanol or butyrate), appreciable amounts of glucose were formed from hydroxypyruvate. A possible explanation for this phenomenon is discussed.

Iron deficiency decreases gluconeogenesis in isolated rat hepatocytes

1989 ◽  
Vol 67 (5) ◽  
pp. 1868-1872 ◽  
Author(s):  
K. L. Klempa ◽  
W. T. Willis ◽  
R. Chengson ◽  
P. R. Dallman ◽  
G. A. Brooks
Keyword(s):  
Iron Deficiency ◽  
Glucose Production ◽  
Rat Hepatocytes ◽  
Female Rats ◽  
Glucose Turnover ◽  
Dietary Iron ◽  
Isolated Rat Hepatocytes ◽  
Iron Deficient ◽  
Isolated Rat

Dietary iron deficiency in rats results in increased blood glucose turnover and recycling. We measured the rates of glucose production in isolated hepatocytes from iron-sufficient (Fe+) and iron-deficient (Fe-) rats to assess the intrinsic capacity of the Fe- liver to carry out gluconeogenesis. Low-iron and control diets were given to 21-day-old female rats. After 4-5 wk, hemoglobin concentrations averaged 4.1 g/dl in the Fe- and 14.3 g/dl in the Fe+ animals. In the hepatocytes from Fe- rats, there was a 35% decrease in the rate of glucose production from 1 mM pyruvate + 10 mM lactate, a 48% decrease from 0.1 mM pyruvate + 1 mM lactate, a 39% decrease from 1 mM alanine, and a 48% decrease from 1 mM glycerol. The addition of 5 microM norepinephrine or 0.5 microM glucagon to the incubation media produced stimulatory effects on hepatocytes from both Fe- and Fe+ rats, resulting in the maintenance of an average difference of 38% in the rates of gluconeogenesis between the two groups. Studies on isolated liver mitochondria and cytosol revealed alpha-glycerophosphate-cytochrome c reductase and phospho(enol)pyruvate carboxykinase activities to be decreased by 27% in Fe- rats. We conclude that because severe dietary iron deficiency decreases gluconeogenesis in isolated rat hepatocytes, the increased gluconeogenesis demonstrated by Fe- rats in vivo is attributable to increased availability of gluconeogenic substrates and upregulation of the pathway.

scholarly journals Glucose Production by Isolated Rat Liver Cells

1961 ◽  
Vol 236 (5) ◽  
pp. 1247-1252 ◽  
Author(s):  
William J. Rutter ◽  
Ronald W. Brosemer
Keyword(s):  
Rat Liver ◽  
Glucose Production ◽  
Liver Cells ◽  
Isolated Rat Liver ◽  
Rat Liver Cells ◽  
Isolated Rat

Growth hormone acutely increases glucose output by hepatocytes isolated from hypophysectomized rats

1989 ◽  
Vol 122 (2) ◽  
pp. 457-464 ◽  
Author(s):  
W. L. Blake ◽  
S. D. Clarke
Keyword(s):  
Fatty Acid ◽  
Rat Liver ◽  
Fatty Acid Synthesis ◽  
Acid Synthesis ◽  
Liver Cells ◽  
Maximal Response ◽  
Isolated Rat Hepatocytes ◽  
Rat Liver Cells ◽  
Hypophysectomized Rats ◽  
Glucose Output

ABSTRACT A series of experiments using isolated rat hepatocytes was carried out to establish rat liver cells in suspension as a physiological model for examining GH responses, and to determine whether acute recombinant bovine GH (rbGH) treatment of rat liver cells increased glucose output and/or suppressed fatty acid synthesis from lactate. Rat liver cells were isolated by collagenase perfusion and incubated in short-term (<60 min) suspension. The amount of insulin, glucagon or vasopressin required to elicit a half-maximal response was within the physiological range of the circulating hormone. When hepatocytes from normal rats were acutely (<60 min) treated with 0, 0·1, 10, 100 or 1000 nmol rbGH/l, rates of hepatocyte glucose output and fatty acid synthesis were unaltered. In addition, acute rbGH treatment (1000 nmol/l) did not alter hepatocyte responsiveness to insulin or vasopressin. However, acute rbGH treatment of hepatocytes isolated from hypophysectomized rats significantly (P < 0·05) increased the rate of glucose output twofold and moderately (P<0·10) enhanced fatty acid synthesis. The accelerated rate of glucose production was not accompanied by an increase in the amount of glycogen phosphorylase-a. The observations with liver cells from hypophysectomized rats are not consistent with a GH receptor-transducing mechanism which is like that for glucagon (adenylate cyclase-linked) or insulin (tyrosine kinase-linked). Journal of Endocrinology (1989) 122, 457–464

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