scholarly journals The role of prolactin and progesterone in the regulation of lipogenesis in maternal and foetal rat liver in vivo and in isolated hepatocytes during the last day of gestation

1986 ◽  
Vol 239 (1) ◽  
pp. 135-139 ◽  
Author(s):  
M Lorenzo ◽  
C Roncero ◽  
M Benito
Keyword(s):  
Rat Liver ◽  
Lipid Synthesis ◽  
Isolated Hepatocytes ◽  
Hepatic Lipogenesis ◽  
Treatment Conditions ◽  
Foetal Liver ◽  
Foetal Rat

The administration of progesterone on day 21 of gestation increases the rates of lipogenesis in the liver in vivo and in hepatocytes isolated from rats on day 22 of pregnancy. Bromocriptine administration increases the rates of hepatic lipogenesis in vivo, but has no effect on lipid synthesis in hepatocytes under the same treatment conditions. Concurrently, the administration of progesterone or bromocriptine on day 21 to the mother increases the rates of lipogenesis in the foetal liver in vivo on day 22. The rates of lipid synthesis in foetal isolated hepatocytes are increased by progesterone administration, but remain unchanged by bromocriptine.

scholarly journals The development of gluconeogenesis in rat liver. Effects of glucagon and ether

1970 ◽  
Vol 120 (2) ◽  
pp. 385-392 ◽  
Author(s):  
Helen Philippidis ◽  
F. J. Ballard
Keyword(s):  
Rat Liver ◽  
Redox State ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Fold Increase ◽  
Similar Increase ◽  
Ether Anaesthesia ◽  
Foetal Liver ◽  
Foetal Rat ◽  
Newborn Animals

1. Administration of glucagon to foetal rats produced a 10–15-fold increase in hepatic phosphoenolpyruvate carboxykinase activity together with a similar increase in the overall pathway of pyruvate conversion into glycogen in liver slices. 2. Glucagon was without effect on gluconeogenesis in vivo, which remained at approx. 0.1% of the incorporation as measured in newborn animals. 3. The apparent discrepancy between these results was due to the ether anaesthesia that was required for experimentation in vivo. Under conditions when minimal ether was used, the rates of labelling of glycogen from [3-14C]pyruvate in vivo were increased 10–20-fold and there was an additional stimulus by glucagon. 4. Ether anaesthesia produced a more reduced redox state of the foetal liver cytosol and lowered the ATP/ADP concentration ratio. 5. It is proposed that these effects are significant in the limitation of gluconeogenesis in the foetal rat liver, so that only with high phosphoenolpyruvate carboxykinase activity, high ATP concentration and a relatively oxidized cytosol redox state will a functional gluconeogenic pathway be present.

scholarly journals The role of glycogen synthase phosphatase in the glucocorticoid-induced deposition of glycogen in foetal rat liver

1980 ◽  
Vol 192 (2) ◽  
pp. 607-612 ◽  
Author(s):  
F Vanstapel ◽  
F Doperé ◽  
W Stalmans
Keyword(s):  
Rat Liver ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Late Gestation ◽  
Adult Liver ◽  
Foetal Liver ◽  
Foetal Rat ◽  
Experimental Approaches ◽  
Protein Components

1. The mechanism that underlies the induction of glycogen synthesis in the foetal rat liver by glucocorticoids was reinvestigated in conditions where the accumulation of glycogen is either precociously induced with dexamethasone or inhibited by steroid deprivation. It appears that glucocorticoids act as the physiological trigger for glycogen synthesis by inducing both glycogen synthase (a known effect) and its activating enzyme, glycogen synthase phosphatase. 2. The activity of glycogen synthase phosphatase in adult liver stems from the interaction of two protein components [Doperé, Vanstapel & Stalmans (1980) Eur. J. Biochem. 104, 137–146]. Two independent experimental approaches indicate that the cytosolic ‘S-component’ is already well developed in the foetal liver before the onset of glycogen synthesis. The manifold glucocorticoid-dependent increase in synthase phosphatase activity during late gestation must be attributed to the specific development of the glycogen-bound ‘G-component’.

scholarly journals Regulation of the expression of the mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase gene. Its role in the control of ketogenesis

1992 ◽  
Vol 283 (1) ◽  
pp. 261-264 ◽  
Author(s):  
N Casals ◽  
N Roca ◽  
M Guerrero ◽  
G Gil-Gómez ◽  
J Ayté ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
Rat Liver ◽  
Genetic Expression ◽  
Fat Feeding

We have explored the role of mitochondrial 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase in regulating ketogenesis. We had previously cloned the cDNA for mitochondrial HMG-CoA synthase and have now studied the regulation in vivo of the expression of this gene in rat liver. The amount of processed mitochondrial HMG-CoA synthase mRNA is rapidly changed in response to cyclic AMP, insulin, dexamethasone and refeeding, and is greatly increased by starvation, fat feeding and diabetes. We conclude that one point of ketogenic control is exercised at the level of genetic expression of mitochondrial HMG-CoA synthase.

Regulation of glucose production in rainbow trout: role of epinephrine in vivo and in isolated hepatocytes

2000 ◽  
Vol 278 (4) ◽  
pp. R956-R963 ◽  
Author(s):  
Jean-Michel Weber ◽  
Deena S. Shanghavi
Keyword(s):  
Rainbow Trout ◽  
Hepatic Glucose Production ◽  
Glucose Production ◽  
Isolated Hepatocytes ◽  
Relative Increase ◽  
Dependent Manner ◽  
Rainbow Trout Oncorhynchus Mykiss

The rate of hepatic glucose production (Ra glucose) of rainbow trout ( Oncorhynchus mykiss) was measured in vivo by continuous infusion of [6-3H]glucose and in vitro on isolated hepatocytes to examine the role of epinephrine (Epi) in its regulation. By elevating Epi concentration and/or blocking β-adrenoreceptors with propranolol (Prop), our goals were to investigate the mechanism for Epi-induced hyperglycemia to determine the possible role played by basal Epi concentration in maintaining resting Ra glucose and to assess indirect effects of Epi in the intact animal. In vivo infusion of Epi caused hyperglycemia (3.75 ± 0.16 to 8.75 ± 0.54 mM) and a twofold increase in Ra glucose (6.57 ± 0.79 to 13.30 ± 1.78 μmol ⋅ kg− 1 ⋅ min− 1, n = 7), whereas Prop infusion decreased Ra from 7.65 ± 0.92 to 4.10 ± 0.56 μmol ⋅ kg− 1 ⋅ min− 1( n = 10). Isolated hepatocytes increased glucose production when treated with Epi, and this response was abolished in the presence of Prop. We conclude that Epi-induced trout hyperglycemia is entirely caused by an increase in Ra glucose, because the decrease in the rate of glucose disappearance normally seen in mammals does not occur in trout. Basal circulating levels of Epi are involved in maintaining resting Ra glucose. Epi stimulates in vitro glucose production in a dose-dependent manner, and its effects are mainly mediated by β-adrenoreceptors. Isolated trout hepatocytes produce glucose at one-half the basal rate measured in vivo, even when diet, temperature, and body size are standardized, and basal circulating Epi is responsible for part of this discrepancy. The relative increase in Ra glucose after Epi stimulation is similar in vivo and in vitro, suggesting that indirect in vivo effects of Epi, such as changes in hepatic blood flow or in other circulating hormones, do not play an important role in the regulation of glucose production in trout.

IL-4 increases surfactant and regulates metabolism in vivo

2000 ◽  
Vol 278 (1) ◽  
pp. L75-L80 ◽  
Author(s):  
Machiko Ikegami ◽  
Jeffrey A. Whitsett ◽  
Zissis C. Chroneos ◽  
Gary F. Ross ◽  
Jacquelyn A. Reed ◽  
...  
Keyword(s):  
Lipid Synthesis ◽  
Fold Increase ◽  
Surfactant Protein ◽  
Clara Cells ◽  
Wild Type ◽  
Surfactant Lipid ◽  
Alveolar Proteinosis ◽  
Selective Increase

Mice that express interleukin (IL)-4 in Clara cells (CCSP-IL-4) develop chronic airway inflammation and an alveolar proteinosis-like syndrome. To identify the role of IL-4 in surfactant homeostasis, we measured lipid and protein metabolism in the lungs of CCSP-IL-4 mice in vivo. Alveolar saturated phosphatidylcholine (Sat PC) pools were increased 6.5-fold and lung tissue Sat PC pools were increased 4.8-fold in the IL-4 transgenic mice. Whereas surfactant protein (SP) A was increased proportionately to Sat PC, SP-D was increased approximately 90-fold in the IL-4 mice compared with wild-type mice and was associated with 2.8-fold increase in SP-D mRNA. The incorporation of palmitate and choline into Sat PC was increased about twofold in CCSP-IL-4 mice. Although trace doses of radiolabeled Sat PC were cleared from the air spaces and lungs of CCSP-IL-4 mice more slowly than in wild-type mice, net clearance of Sat PC from the lungs of CCSP-IL-4 mice was sixfold higher in the IL-4 mice than in wild-type mice because of the larger Sat PC pool sizes. Expression of IL-4 in Clara cells increased surfactant lipid synthesis and clearance, establishing a new equilibrium with increased surfactant pools and an alveolar proteinosis associated with a selective increase in SP-D protein, demonstrating a previously unexpected effect of IL-4 in pulmonary surfactant homeostasis.

scholarly journals Polyribosomes in isolated liver cells. Preparative procedures, effects of incubation and correlation with protein synthesis

1980 ◽  
Vol 186 (1) ◽  
pp. 35-45 ◽  
Author(s):  
A J Dickson ◽  
C I Pogson
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Isolated Hepatocytes ◽  
Liver Cells ◽  
Liver Protein ◽  
Isolated Cells ◽  
Isolated Liver Cells ◽  
Rat Liver Cells ◽  
Isolated Liver

Methods have been derived which permit the isolation of undergraded polyribosomes from isolated rat liver cells. Under the conditions used the polyribosome profile of hepatocytes immediately after isolation was essentially identical with that from intact liver. However, during incubation of cells in complex physiological media there was a progressive dissociation of polyribosomes. The addition of a variety of factors that produce reaggregation of polyribosomes in rat liver in vivo did not prevent dissociation during cell incubations. Although large polyribosomes were lost most rapidly, the albumin-synthesizing capacity of isolated cells was not selectively lost when compared with total protein synthesis. The significance of these results for the use of isolated hepatocytes in the study of liver protein synthesis is discussed.

scholarly journals Possible role of histone acetylation and histone H1° replacement for the initiation of replication in regenerating rat liver

1991 ◽  
Vol 280 (3) ◽  
pp. 777-781
Author(s):  
G Weiss ◽  
H Talasz ◽  
B Puschendorf
Keyword(s):  
Dna Synthesis ◽  
Histone Acetylation ◽  
Rat Liver ◽  
Histone Acetyltransferase ◽  
Histone H1 ◽  
Acetyltransferase Activity ◽  
Initiation Of Replication ◽  
Histone Acetyltransferase Activity

The role of histone acetylation and DNA synthesis has been investigated extensively in the regenerating rat liver system in the presence and absence of the cyclophosphamide derivative mafosfamide. We demonstrate a mafosfamide-induced inhibition of maximum histone acetyltransferase activity followed by a second elevation of enzyme activity and an accompanying total suppression of DNA synthesis for 7-8 h. The maximum of histone acetyltransferase activity, in parallel with an elevated acetylation in vivo, the consecutive replacement of histone H1(0) amd initiation of replication occur sequentially in the presence and absence of mafosfamide, but with a temporary delay of 7-8 h. Our data indicate that modifications of histone acetyltransferase (EC 2.3.1.48) activity do not significantly influence the acetylation patterns of histones H3 and H4. The mafosfamide-induced change of histone acetyltransferase activity and acetylation in vivo, the shift of histone H1(0) exchange and the consecutive transition of initiation of replication suggest that these three events might be functionally related.

scholarly journals Studies on the activation of rat liver pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase by adrenaline and glucagon. Role of increases in intramitochondrial Ca2+ concentration

1985 ◽  
Vol 231 (3) ◽  
pp. 597-608 ◽  
Author(s):  
J G McCormack
Keyword(s):  
Rat Liver ◽  
Pyruvate Dehydrogenase ◽  
Liver Mitochondria ◽  
Active Enzyme ◽  
Female Rats ◽  
Rat Liver Mitochondria ◽  
Na Ions ◽  
Oxoglutarate Dehydrogenase

The administration in vivo of either adrenaline or glucagon alone resulted in increases of about 2-fold in the amounts of active, non-phosphorylated, pyruvate dehydrogenase in the livers of fed male or female rats, whereas when administered together increases of about 4-fold were obtained. Ca2+-dependent increases in the amount of active enzyme of up to about 5-fold could be achieved in isolated rat liver mitochondria by incubating them with increasing extramitochondrial [Ca2+]; from this, two conditions of Ca loading were chosen which caused increases in active enzyme similar to those with the hormone treatments given above. The increases in enzyme activity owing to these Ca loads persisted through the ‘re-isolation’ of mitochondria and their incubation in Na+-free KCl-based media containing EGTA. Differences from values obtained with unloaded controls could be diminished by adding Na+ ions to cause the egress of Ca2+ from the mitochondria, or enough extramitochondrial Ca2+ to saturate the enzyme in its Ca2+-dependent activation; the effects of Na+ could be blocked by diltiazem, an inhibitor of mitochondrial Na+/Ca2+ exchange. The re-isolated, Ca-preloaded, mitochondria also exhibited enhanced activities of 2-oxoglutarate dehydrogenase when assayed at non-saturating [2-oxoglutarate] by two different methods; effects of Na+, Ca2+ or diltiazem on the persistent activations of this enzyme were similar to those for pyruvate dehydrogenase. Na+ caused a marked depletion, which could be blocked by diltiazem, of the 45Ca content of re-isolated mitochondria which had pre-loaded with Ca, containing 45Ca, to the same degrees as above. The activities of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase in incubated liver mitochondria prepared from rats subjected to the hormone treatments given above were found to behave in a very similar manner to those exhibited in the re-isolated, Ca-preloaded, mitochondria. It is concluded that these hormones each bring about the activations of these rat liver enzymes by causing increases in intramitochondrial [Ca2+], and that their effects, as such, are additive.

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