scholarly journals Effect of diethylstilboestrol on phosphatidylcholine biosynthesis and choline metabolism in the liver of roosters

1981 ◽  
Vol 200 (2) ◽  
pp. 321-326 ◽  
Author(s):  
C Vigo ◽  
D E Vance
Keyword(s):  
Portal Vein ◽  
Fold Increase ◽  
Hormone Treatment ◽  
Phospholipid Metabolism ◽  
Choline Kinase ◽  
Control Value ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Choline Metabolism ◽  
Phosphatidylcholine Biosynthesis

It has been known for 40 years that oestrogens stimulate phospholipid metabolism in roosters. We have investigated in vivo the mechanism for this effect. Young roosters were injected daily with 1 mg of diethylstilboestrol for 1--3 days. At 4 h after the last injection, 30 microCi of [Me-3H]choline was injected into the portal vein. At periods up to 3 min the livers were freeze-clamped and choline and its metabolites were extracted and resolved by t.l.c. Hormone treatment in the first 2 days resulted in a 2-fold increase in phosphorylation of [Me-3H]choline and a decrease in the oxidation of [Me-3H]choline to [3H]betaine. The concentrations of phosphocholine in liver were increased 2-fold during the first 2 days concomitant with a 2-fold increase in the rate of phosphatidylcholine biosynthesis. After 3 days of hormone treatment, many of the above effects were reversed and the rate of phosphatidylcholine biosynthesis decreased to approx. 60% of the control value. The results suggest that the initial hormone treatments activate choline kinase within 4 h and, thereby, divert choline form oxidation to betaine. The resulting increased phosphocholine concentrations cause an increase in the activity of CTP:phosphocholine cytidylyltransferase, which results in a doubling of the rate of phosphatidylcholine biosynthesis. After 3 days of hormone treatment, the biosynthesis of phosphatidylcholine is decreased, most likely by an effect on the cytidylyltransferase reaction.

Influence of C-ANF receptor and neutral endopeptidase on pharmacokinetics of ANF in rats

1991 ◽  
Vol 260 (1) ◽  
pp. R208-R216 ◽  
Author(s):  
P. J. Chiu ◽  
G. Tetzloff ◽  
M. T. Romano ◽  
C. J. Foster ◽  
E. J. Sybertz
Keyword(s):  
High Performance ◽  
Fold Increase ◽  
Neutral Endopeptidase ◽  
Volume Of Distribution ◽  
Fourfold Increase ◽  
Control Value ◽  
Enzymatic Pathways ◽  
Hydrolysis Of

The role of C-atrial natriuretic factor (ANF) receptors and neutral endopeptidase (NEP) in the pharmacokinetics and hydrolysis of 125I-labeled ANF was evaluated in rats by using C-ANF and SCH 39370 to block the nonenzymatic and enzymatic pathways, respectively. After a bolus injection of 125I-ANF, the resulting area under the plasma concentration curve (AUC) with C-ANF treatment was seven times the control value with regard to trichloroacetic acid-precipitable (TCA-ppt) radioactivity (intact ANF). SCH 39370 tended to increase AUC, but the changes were not significant. Nevertheless, SCH 39370 suppressed the appearance of TCA-soluble radioactivity (hydrolytic products), indicating that in vivo inhibition of ANF degradation had occurred. SCH 39370 plus C-ANF produced a 15-fold increase in AUC for TCA-ppt radioactivity and a reduction in plasma TCA-soluble radioactivity. High-performance liquid chromatography (HPLC) analysis confirmed that combination treatment increased intact ANF and reduced hydrolytic products in the plasma. SCH 39370 reduced clearance (C) without altering volume of distribution in steady state (Vss) and half-life (t1/2). C-ANF decreased both C and Vss leading to a fourfold increase in t1/2, which was further prolonged by SCH 39370 (7.5 times control). Bilateral nephrectomy caused a proportionally similar decrease in Vss and C without changing t1/2, suggesting significant extrarenal metabolism of ANF. SCH 39370 systemically inhibits ANF hydrolysis; the resulting increase in ANF, however, is masked by the great capacity of ANF clearance receptors but can be revealed with excess C-ANF, suggesting that the plasma ANF concentrations are determined by the interplay of the C-ANF receptor and NEP systems.

scholarly journals N-[2-bromocinnamyl(amino)ethyl]-5-isoquinolinesulphonamide (H-89) inhibits incorporation of choline into phosphatidylcholine via inhibition of choline kinase and has no effect on the phosphorylation of CTP:phosphocholine cytidylyltransferase

1994 ◽  
Vol 297 (1) ◽  
pp. 241-247 ◽  
Author(s):  
M Wieprecht ◽  
T Wieder ◽  
C C Geilen
Keyword(s):  
Cell Culture ◽  
Kinase Activity ◽  
Inhibitory Effect ◽  
Selective Inhibitor ◽  
Choline Kinase ◽  
Dependent Protein Kinase ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Phosphatidylcholine Biosynthesis ◽  
Dependent Protein

We have shown previously that N-[2-bromocinnamyl(amino)-ethyl]-5-isoquinolinesulphonamide (H-89), a selective inhibitor of cyclic-AMP-dependent protein kinase (PKA), inhibits phosphatidylcholine biosynthesis in HeLa cells. In the present study, we elucidated the mechanism underlying the described inhibition. Treatment of cells with 10 microM H-89 had no effect on the phosphorylation of CTP:phosphocholine cytidylyltransferase. However, H-89 slightly affected the distribution of cytidylyltransferase between cytosol and membranes, but the cellular 1,2-diacylglycerol content was not influenced. Furthermore, pulse-chase experiments revealed that H-89 did not affect cytidylyltransferase activity. Instead, H-89 inhibited choline kinase, the enzyme catalysing the first step in the CDP-choline pathway. In the presence of 10 microM H-89, choline kinase activity was inhibited by 36 +/- 7.6% in vitro. Additionally, the phosphorylation of choline to phosphocholine was inhibited by 30 +/- 3% in cell-culture experiments. This inhibitory effect could be partly prevented by simultaneous addition of 10 microM forskolin, indicating that choline kinase is regulated in part by PKA activity.

Effects of variation of the tri-iodothyronine/reverse triiodothyronine ratio in vivo on the metabolic characteristics of subsequently isolated hepatocytes

1987 ◽  
Vol 72 (4) ◽  
pp. 511-513
Author(s):  
A. Al-Saadi ◽  
D. Sprague ◽  
M. Sugden ◽  
A. Goode ◽  
S. Orr
Keyword(s):  
Body Weight ◽  
Glucose Production ◽  
Fold Increase ◽  
Isolated Hepatocytes ◽  
Major Product ◽  
Control Value ◽  
Metabolic Characteristics ◽  
Reverse Triiodothyronine ◽  
14Co2 Release

1. Reverse tri-iodothyronine (3,3′,5′-tri-iodothyronine, rT3), a major product of the peripheral monodeiodination of thyroxine, was administered subcutaneously to fed rats at a dose of 100 μg/100 g body weight for 2 consecutive days. 2. This dose induced a 17-fold increase in plasma rT3 (from 0.05±sem 0.01 to 0.85±0.11 ng/ml, P > 0.001) whilst the plasma T3 concentration was decreased to half of the control value (0.40 ± 0.03 to 0.20 ± 0.02 ng/ml, P > 0.01). 3. As a result of these changes the T3/rT3 ratio was therefore decreased from 8.0 ±1.6 to 0.23 ± 0.03 (P > 0.001). 4. Hepatocytes prepared from control or rT3treated rats were incubated with [l-14C]oleate and the rates of 14CO2 release and glucose production were estimated. Despite the changes in ratio of T3 to rT3 observed in vivo, rates of 14CO2 release and glucose production rate from hepatocytes subsequently isolated were unchanged.

scholarly journals Overexpression of phosphatidylethanolamine N-methyltransferase 2 in CHO-K1 cells does not attenuate the activity of the CDP-choline pathway for phosphatidylcholine biosynthesis

1996 ◽  
Vol 320 (3) ◽  
pp. 905-910 ◽  
Author(s):  
Mark W. LEE ◽  
Marica BAKOVIC ◽  
Dennis E. VANCE
Keyword(s):  
Cell Lines ◽  
Chinese Hamster Ovary ◽  
Cho Cells ◽  
Protein Level ◽  
Chinese Hamster ◽  
Immunoblot Analysis ◽  
Phospholipid Metabolism ◽  
Enzymic Activity ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Phosphatidylcholine Biosynthesis

Chinese hamster ovary (CHO) cells express only a trace amount of phosphatidylethanolamine N-methyltransferase (PEMT) activity. CHO cells make their phosphatidylcholine (PC) via the CDP-choline pathway. We investigated whether or not overexpression of PEMT2, an isoform of PEMT, in these cells would down-regulate the activity of the CDP-choline pathway. Transfection of CHO cells with PEMT2 cDNA behind the cytomegalovirus promoter resulted in a series of cell lines that overexpressed PEMT2. Phospholipid metabolism was characterized in cell lines that expressed a medium (281 pmol/min per mg of protein) and a high (1300 pmol/min per mg of protein) level of PEMT activity. The expression of the regulated enzyme (CTP:phosphocholine cytidylyltransferase) in the CDP-choline pathway was increased, not decreased, in these cell lines as judged by immunoblot analysis and enzymic activity. Conversion of phosphatidylethanolamine to PC was enhanced in CHO cells that expressed PEMT2 activity. PC mass was not increased in the transfected compared with the control cells. The rate of PC catabolism made by either the CDP-choline or methylation pathways was unaffected by PEMT2 expression. We conclude that expression of PEMT2 in CHO cells does not down-regulate, but rather enhances, the expression of CTP:phosphocholine cytidylyltransferase.

Effects of fatty acids on phosphatidylcholine biosynthesis in isolated hamster heart

1986 ◽  
Vol 64 (5) ◽  
pp. 413-417 ◽  
Author(s):  
Thomas Mock ◽  
Tracy L. Slater ◽  
Gilbert Arthur ◽  
Alvin C. Chan ◽  
Patrick C. Choy
Keyword(s):  
Fatty Acids ◽  
Stearic Acid ◽  
Microsomal Fraction ◽  
Rat Hepatocytes ◽  
Free Form ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Phosphatidylcholine Biosynthesis ◽  
Hamster Heart ◽  
Arachidonic Acids

The effects of stearic, oleic, and arachidonic acids on phosphatidylcholine biosynthesis in the hamster heart were investigated. When hamster hearts were perfused with labelled choline in the presence of fatty acids, biosynthesis of phosphatidylcholine was stimulated only by stearic acid. Stearic acid was found to accumulate in unesterified (free) form in the hamster heart after perfusion. The stimulation by stearic acid was mediated in vivo by an enhancement of CTP:phosphocholine cytidylyltransferase activity in the microsomal fraction of the hamster heart and the enzyme activity in the cytosolic fraction was not affected. In contrast with the observations in rat hepatocytes, cytidylyltransferase from the hamster heart was not stimulated directly by stearic acid. The selective activation of the microsomal enzyme when the heart was perfused with stearic acid suggests that activation of the enzyme was mediated via the modification of the membrane by stearic acid.

Activities of the phosphatidylcholine biosynthetic enzymes in rat liver during development

1983 ◽  
Vol 61 (10) ◽  
pp. 1147-1152 ◽  
Author(s):  
Steven L. Pelech ◽  
Ellen Power ◽  
Dennis E. Vance
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Specific Activity ◽  
Perinatal Period ◽  
Choline Kinase ◽  
Specific Enzyme ◽  
Methyltransferase Activity ◽  
Specific Enzyme Activity ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Phosphatidylcholine Biosynthesis

The activities of the enzymes of rat hepatic phosphatidylcholine biosynthesis have been measured as a function of development in the rat (term, 23 days). During the last 5 days of gestation, the specific activity of choline kinase was elevated almost fivefold (p < 0.05). After parturition, choline kinase activity was reduced to adult values by the 5th postnatal day. Over 75% of the total CTP:phosphocholine cytidylyltransferase protein in prenatal liver was detected in the cytosolic fraction. On the day of birth, most of the cytidylyltransferase translocated to the microsomes so that the microsomal specific enzyme activity was 3.3-fold higher (p < 0.01) and the cytosolic specific enzyme activity (measured in the presence of phospholipid) was 68% lower (p < 0.001) than the day before parturition. CDPcholine:diacylglycerol cholinephosphotransferase activity (measured in the presence of diacylglycerol) increased 130-fold (p < 0.001) during the last 5 days of gestation. On the 10th postnatal day, cholinephosphotransferase activity was 1.7-fold higher (p < 0.001) than immediately after birth, but declined to adult values by the 19th day. Between the 5th day prior to parturition and the 10th postnatal day, phosphatidylethanolamine N-methyltransferase activity steadily increased 16-fold (p < 0.001). The results are in agreement with the hypothesis that the increase in phosphatidylcholine in rat liver during the perinatal period is due to an increased synthesis of CDPcholine, which is a consequence of the translocation of the cytidylyltransferase from cytosol to the endoplasmic reticulum.

scholarly journals Pleiotropic Alterations in Lipid Metabolism in Yeastsac1Mutants: Relationship to “Bypass Sec14p” and Inositol Auxotrophy

1999 ◽  
Vol 10 (7) ◽  
pp. 2235-2250 ◽  
Author(s):  
Marcos P. Rivas ◽  
Brian G. Kearns ◽  
Zhigang Xie ◽  
Shuling Guo ◽  
M. Chandra Sekar ◽  
...  
Keyword(s):  
Phospholipase D ◽  
Phospholipid Metabolism ◽  
Metabolic Phenotype ◽  
Transcriptional Expression ◽  
Pathway Activity ◽  
Transfer Protein ◽  
Phosphatidylcholine Biosynthesis ◽  
Phosphatidylinositol Transfer ◽  
Phosphatidylinositol 4

SacIp dysfunction results in bypass of the requirement for phosphatidylinositol transfer protein (Sec14p) function in yeast Golgi processes. This effect is accompanied by alterations in inositol phospholipid metabolism and inositol auxotrophy. Elucidation of how sac1mutants effect “bypass Sec14p” will provide insights into Sec14p function in vivo. We now report that, in addition to a dramatic accumulation of phosphatidylinositol-4-phosphate,sac1 mutants also exhibit a specific acceleration of phosphatidylcholine biosynthesis via the CDP-choline pathway. This phosphatidylcholine metabolic phenotype is sensitive to the two physiological challenges that abolish bypass Sec14p insac1 strains; i.e. phospholipase D inactivation and expression of bacterial diacylglycerol (DAG) kinase. Moreover, we demonstrate that accumulation of phosphatidylinositol-4-phosphate in sac1mutants is insufficient to effect bypass Sec14p. These data support a model in which phospholipase D activity contributes to generation of DAG that, in turn, effects bypass Sec14p. A significant fate for this DAG is consumption by the CDP-choline pathway. Finally, we determine that CDP-choline pathway activity contributes to the inositol auxotrophy of sac1 strains in a novel manner that does not involve obvious defects in transcriptional expression of theINO1 gene.

Impaired phosphatidylcholine biosynthesis does not attenuate liver regeneration after 70% partial hepatectomy in hepatic CTP:phosphocholine cytidylyltransferase-α deficient mice

2012 ◽  
Vol 90 (10) ◽  
pp. 1403-1412 ◽  
Author(s):  
Ji Ling ◽  
Lin Fu Zhu ◽  
Dennis E. Vance ◽  
René L. Jacobs
Keyword(s):  
Liver Regeneration ◽  
Partial Hepatectomy ◽  
Hepatocyte Proliferation ◽  
Phosphocholine Cytidylyltransferase ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Phosphatidylcholine Biosynthesis ◽  
Murine Liver ◽  
Proliferation Of Hepatocytes

Phosphatidylcholine (PC) is the major component of mammalian membranes, and the induction of PC biosynthesis has been shown to be an essential step in cell proliferation in various cell lines. Cytidine triphosphate (CTP):phosphocholine cytidylyltransferase α (CTα) regulates the primary pathway of PC biosynthesis in the liver. The targeted disruption of CTα in murine liver (LCTα−/− mice) decreases hepatic PC mass and the number of cells in the liver, suggesting CTα as an important factor for hepatocyte proliferation. To elucidate the role of CTα in hepatic cell division in vivo, we monitored liver regeneration after 70% partial hepatectomy in LCTα−/− and loxP flanked (floxed) LCTα (control) mice. To our surprise, liver re-growth, DNA synthesis, and PC mass after surgery were not impaired in LCTα−/− mice, despite reduced total PC synthesis. Furthermore, PC synthesis in the control mice was not induced after 70% partial hepatectomy. We conclude that CTα is not essential for proliferation of hepatocytes in vivo, and that basal hepatic PC biosynthesis is sufficient to sustain regeneration after 70% partial hepatectomy.

scholarly journals Control of phosphatidylcholine synthesis and the regulatory role of choline kinase in rat liver. Evidence from essential-fatty acid-deficient rats

1978 ◽  
Vol 176 (2) ◽  
pp. 631-633 ◽  
Author(s):  
J P Infante ◽  
J E Kinsella
Keyword(s):  
Fatty Acid ◽  
Essential Fatty Acid ◽  
Rat Liver ◽  
Specific Activity ◽  
Fold Increase ◽  
Regulatory Role ◽  
Choline Kinase ◽  
Fatty Acid Deficiency

Choline kinase and phosphocholine cytidylytransferase catalyse the rate-limiting steps of the cytidine pathway for the synthesis of phosphatidylcholine [Infante (1977) Biochem. J. 167, 847–849]. Essential-fatty acid deficiency induces a 3.5-fold increase in the specific activity of choline kinase, whereas the specific activity of the cytidylytransferase remains unchanged in rat liver. This change in specific activity accounts for the calculated increase in flux through the cytidine pathway produced in vivo by the same dietary state [Trewhella & Collins (1973 Biochim. Biophys. Acta 296, 34–50], thus confirming the fact that choline kinase has a regulatory role in the cytidine pathway for the synthesis of phosphatidylcholine.

Semliki Forest virus does not inhibit phosphatidylcholine biosynthesis in BHK-21 cells

1981 ◽  
Vol 59 (1) ◽  
pp. 38-47 ◽  
Author(s):  
Frederick W. Whitehead ◽  
Everard Trip ◽  
Dennis E. Vance
Keyword(s):  
Semliki Forest Virus ◽  
Choline Kinase ◽  
Bhk Cells ◽  
G Cells ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Phosphatidylcholine Biosynthesis ◽  
Infected Cells ◽  
Specific Activities

The mechanism by which Semliki Forest virus inhibits the incorporation of [methyl-3H]- choline into phosphatidylcholine has been investigated. Decreased labeling of the lipid was not due to altered uptake of [methyl-3H]choline. The specific activities of choline kinase and CTP:phosphocholine cytidylyltransferase were unchanged. The previously observed inhibition (Vance, D. E. &Burke, D. C. (1974) Eur. J. Biochem. 43, 327–336) of CDP-choline:1,2-diacylglycerol phosphocholinetransferase was confirmed. Since the decreased activity of the phosphocholinetransferase may not have caused the reduced labeling of phosphatidylcholine, the amounts of this lipid and its precursors were measured. We observed changes in the concentration of phosphocholine (34 ± 12 and 120 ± 40 nmol∙g cells−1 in mock- and virus infected cells, respectively) and CTP (116 ± 35 and 36 ± 13 nmol∙g cells−1 in mock- and virus-infected cells, respectively). Pulse–chase studies with [methyl-3H]choline demonstrated that, initially, most of the radioactivity was in phosphocholine. As it disappeared from this compound, it appeared in phosphatidylcholine. From these results, we calculated the rate of phosphatidylcholine biosynthesis to be 0.56 and 1.23 nmol∙min−1∙g cells−1 in mock- and virus-infected BHK-21 cells, respectively. We conclude that phosphatidylcholine biosynthesisis not inhibited in Semliki Forest virus infected BHK cells, but rather is stimulated 6.75 h after infection. The decreased labeling observed during pulse studies with [methyl-3H]choline is due to dilution of the labeled choline into a pool of phosphocholine which is 3.5 times larger in the infected cells.

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