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  • 1
    Electronic Resource
    Electronic Resource
    Gluconeogenesis in rat liver parenchymal cells in primary culture: Permissive effect of the glucocorticoids on glucagon stimulation of gluconeogenesis (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 107 (1981), S. 11-19 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Primary cultures of parenchymal cells isolated from adult rat liver by a collagenase perfusion procedure and maintained as a monolayer in a serum-free culture medium were used to study glucoeogenesis and the role that the glucocorticoids play in the control of this pathway. These cells carried out gluconeogenesis from three-carbon precursors (alanine and lactate) in response to glucagon and dexamethasone added alone or in combination. Maximum glucose production was observed with cells pretreated for several hours with dexamethasone and glucagon prior to addition of substrate and glucagon (8- to 12-fold increase over basal glucose production). Half-maximum stimulation of gluconeogenesis was seen with 3.6 × 10-10 M glucagon and 3.6 × 10-8 M dexamethasone. Maximum stimulation was oberved with 10-7 M glucagon and 10-6 M dexamethasone. The length of time of dexamethasone pretreatment was found to be important in demonstrating the effect of glucocorticoids on glucagon-stimulated gluconeogenesis. Treeatment of cells with dexamethasone for 2 hours did not result in an increase in glucose production over identical experimental conditions in the absence of dexamethasone, wherease pretreatment for 5 hours (1.2-fold increase) or 15 hours (1.7-fold increase) did result in an increase in glucose production. The results establish that the adult rat liver parenchymal cells in primary culture are a valid model system to study hepatic gluconeogenesis. In addition, we have established directly that the glucocorticoids amplify the glucagon stimulation of gluconeogenesis.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041070103
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Coordinate regulation of gluconeogenesis by the glucocorticoids and glucagon: Evidence for acute and chronic regulation by glucagon (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 109 (1981), S. 83-90 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The coordinate regulation of gluconeogenesis by the glucocorticoids and glucagon in primary cultures of adult rat liver parenchymal cells has been studied. The results suggest that glucagon stimulation of glucose production from 3-carbon precursors is composed of at least two components which the glucocorticoids differentially affect. Glucagon treatment of hepatocytes results in an immediate increase in glucose production which is not blocked by cycloheximide and occurs in the absence of any detectable increase of phosphoenolpyruvate carboxykinase activity. This component appears to be regulated by a post-translational mechanism and involves redirection of carbon flow from glycolysis to gluconeogenesis. The second component is characterized by the need for long-term glucagon treatment. This increase in glucose production can be blocked by cycloheximide and is correlated with an increase in phosphoenolpyruvate carbooxykinase activity. The reaction that is accelerated by long-term glucagon incubation is located prior to the triose-phosphate level since long-term incubation with glucagon fails to increase glucose production from dihydroxyacetone any more than does short-term incubation. It is suggested that phosphoenolpyruvate carboxykinase rather than amino acid transport is the key pacemaker reaction in the long-term incubation since the direction and magnitude of the response for glucocorticoid and glucagon stimulation of glucose production is the same whether alanine or lactate is used as the 3-carbon precursor. The glucocorticoids exhibit an additive effect on glucagon-stimulated glucose production for the first component whereas they amplify the second component.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041090110
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  • 3
    Electronic Resource
    Electronic Resource
    Glucagon and choleragen stimulation of glycogenolysis in primary cultures of adult rat liver parenchymal cells: Lack of involvement of the glucocorticoids (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 110 (1982), S. 304-310 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The influence of glucagon, choleragen, and the adrenal glucocorticoids on glycogenolysis in primary cultures of adult rat liver parenchymal cells has been studied. Both glucagon and choleragen caused a twofold to threefold stimulation of glucose production from endogenous reserves of glycogen. The effect of glucagon on glucose production was noted at the earliest time point examined and the stimulation of glucose production was preceded by an elevation of cyclic AMP. Choleragen did not produce a significant stimulation of glucose production until 45 minutes after addition of the agent. Choleragen effects on glucose production were preceded by an elevation of cyclic AMP, but in contrast with glucagon, choleragen did not significantly elevate cyclic AMP until 30 minutes after addition to the culture. One ng of choleragen per ml of medium was sufficient to produce an effect on glucose production. Glucagon- or choleragen-treated cultures mobilized glycogen more rapidly than did untreated cultures incubated in glucose-free medium. In addition, both agents produced a stong inhibition of lactate production. Thus, the stimulation of glucose production by these agents was partially due to increased glycogen mobilization and partially due to redirection of carbon units from glycolysis. That glucose production in the hepatocytes is regulated in part by a cyclic AMP-dependent mechanism is strongly supported by the observation that both agents elevate cyclic AMP and cause an increase in glucose production and inhibition of lactate production. The possibility that the glucocorticoids participated in the regulation of glycogenolysis either in a direct or indirect (permissive) fashion was assessed. It was found that when the direct effect of the glucocorticoids on glycogenesis was taken into account, the glucocorticoids had no direct effects on glycogenolysis, nor did they alter the stimulation of glycogenolysis by glucagon or choleragen.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041100314
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    Paper (German National Licenses)
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