Some studies on the biosynthesis of the molecular species of phosphatidylcholine from rat lung and phosphatidylcholine and phosphatidylethanolamine from rat liver

The possible selectivity of the acyl-CoA:1,2-diacyl-sn-glycerol acyltransferase in rat liver microsomes towards different molecular species of 1,2-diacyl-sn-glycerols was studied. Triacylglycerol synthesis was determined by monitoring the entry of radioactive palmitate from [1-14C]palmitoyl-CoA into triacylglycerol in the presence of various diacylglycerols. The diacylglycerol acyltransferase did not exhibit any selectivity against hexaenoic precursors under the assay conditions used (0.25 mM diacylglycerol in medium) and the rates of triacylglycerol synthesis observed with the various diacylglycerols were not significantly different when the data were analyzed statistically. The results suggest that the extremely low level of docosahexaenoic acid in triacylglycerols cannot be attributed to a discrimination of the diacylglycerol acyltransferase against 1-saturated 2-docosahexaenoyl precursors.

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Incorporation of arachidonic acid into lipids of the isolated perfused rat lung

Journal of Applied Physiology ◽

10.1152/jappl.1989.66.6.2763 ◽

1989 ◽

Vol 66 (6) ◽

pp. 2763-2771 ◽

Cited By ~ 7

Author(s):

F. H. Chilton ◽

J. Y. Westcott ◽

L. M. Zapp ◽

J. E. Henson ◽

N. F. Voelkel

Keyword(s):

Arachidonic Acid ◽

Molecular Species ◽

Mass Spectrometry Analysis ◽

Gas Chromatography Mass Spectrometry ◽

Alveolar Type ◽

Rat Lung ◽

Spectrometry Analysis ◽

Autoradiographic Analysis ◽

Isolated Rat Lung ◽

Stimulation Of

This study has attempted to identify the cells and phosphoglyceride molecular species associated with the rapid turnover of arachidonic acid (AA) in the isolated rat lung. In initial studies, AA complexed to trace amounts of albumin was added to the perfusate of rat lungs for 15 min and the incorporation of [3H]AA into various cells and phosphoglyceride molecular species was determined. Autoradiographic analysis revealed that the AA had labeled endothelial cells but also had already escaped from the intravascular space and labeled epithelial cells including alveolar type II cells. In addition, [3H]AA was found to be incorporated into various phosphoglycerides: phosphatidylcholine (PC) greater than phosphatidylethanolamine (PE) greater than phosphatidylinositol (PI). The majority of this [3H]AA was incorporated into 1-acyl-2-arachidonoyl-sn-glycero-3-PC, -PE, and -PI during the 15-min labeling period. In subsequent experiments, AA remodeling in the lung was examined by pulse labeling with [3H]AA for 15 min, washing unbound AA with albumin, and perfusing for an additional 120 min. In these lungs, some of the [3H]AA was remodeled into 1-alk-1-enyl-acyl-sn-glycero-3-PE. Gas chromatography-mass spectrometry analysis revealed that the largest pools of endogenous AA in the lung are found in PE associated with 1-alk-1-enyl-linked molecular species. On ionophore stimulation of lungs labeled for 15 min, labeled leukotriene (LT) B4, leukotriene C4, and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) were produced. LTC4 had a profoundly different radiospecific activity compared with LTB4 and 6-keto-PGF1 alpha, suggesting a different source of AA as contributing to the production of this eicosanoid.(ABSTRACT TRUNCATED AT 250 WORDS)

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Increased expression of CTP:phosphocholine cytidylyltransferase in maturing type II cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1994.267.1.l25 ◽

1994 ◽

Vol 267 (1) ◽

pp. L25-L32 ◽

Cited By ~ 1

Author(s):

M. Hogan ◽

L. J. Zimmermann ◽

J. Wang ◽

M. Kuliszewski ◽

J. Liu ◽

...

Keyword(s):

Rat Liver ◽

Type Ii Cells ◽

Mrna Levels ◽

Type Ii ◽

Rat Lung ◽

Protein Levels ◽

Ctp:Phosphocholine Cytidylyltransferase ◽

Fetal Rat ◽

Fetal Rat Lung ◽

Phosphatidylcholine Synthesis

We previously reported that phosphatidylcholine synthesis increased in fetal rat lung type II cells with advancing gestation. This increase was accompanied by an increase in CTP:phosphocholine cytidylyltransferase activity, which catalyses a rate regulatory step in de novo phosphatidylcholine synthesis by fetal type II cells. To determine whether this increase in cytidylyltransferase activity is due to an increase in cytidylyltransferase protein levels, the gene and protein expression of cytidylyltransferase was investigated in maturing type II cells. The cytidylyltransferase cDNA was cloned from fetal rat type II cells and showed 99% sequence homology with rat liver cDNA. The cDNA detected two mRNA transcripts (1.8 and 7.5 kb) in fetal rat lung. By reverse-transcriptase polymerase chain reaction (RT-PCR) analysis, cytidyltransferase mRNA content increased three-fold in fetal type II cells with advancing gestation, whereas cytidylyltransferase mRNA levels in fibroblasts remained constant. An antibody against rat liver cytidylyltransferase was used to assess cytidylyltransferase protein. Western blotting revealed that cytidylyltransferase protein content increased threefold in the microsomal fraction of type II cells with advancing gestation. The enzyme protein levels in the cytosolic fraction did not significantly change with development. Enzyme activity studies confirmed these latter observations. We conclude that the increase in surfactant phosphatidylcholine synthesis by type II cells at late fetal gestation is due in part to an increase in the amount of cytidylyltransferase protein.

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Biosynthesis of phosphatidylethanolamines and phosphatidylcholines from ethanolamine and choline in rat liver

Biochemical Journal ◽

10.1042/bj1460309 ◽

1975 ◽

Vol 146 (2) ◽

pp. 309-315 ◽

Cited By ~ 72

Author(s):

R Sundler ◽

B Akesson

Keyword(s):

Rat Liver ◽

Molecular Species ◽

Kinetic Models ◽

Quantitative Data ◽

Specific Radioactivity ◽

Similar Rate ◽

Time Intervals ◽

Previous Suggestion ◽

Kinetics Of

1. The kinetics of phosphatidylcholine and phosphatidylethanolamine synthesis in rat liver were followed 5-60 min after the intraportal injection of [14-C]choline and [3-H]-ethanolamine. 2. At all time-intervals the specific radioactivity of CDP-choline was only about half that of phosphorylcholine. This indicated that CDP-choline was formed at a similar rate from phosphorylcholine and phosphatidylcholines, the latter probably through the reverse reaction of cholinephosphotransferase (EC 2.7.8.2.). In view of recent data obtained from experiments in vitro this implies a significant role for the cholinephosphotransferase reaction in the turnover of molecular species of phosphatidylcholine. 3. The specific radioactivity of CDP-ethanolamine was about twice that of phosphorylethanolamine at all time-intervals studied. This supports a previous suggestion that the liver phosphorylethanolamine pool is subject to compartmentation and shows that there is no rapid equilibration between different pools. In contrast with a recent study, no evidence was found for any significant methylation of phosphoryl-or CDP-ethanolamine to the corresponding choline derivative. 4. Quantitative data on the biosynthesis of molecular species of phosphoLIPIDS via CDP derivatives were calculated according to simple kinetic models. They were in the same range as those calculated from earlier data on precusors incorporated via diacylglycerols. 5. The proportion of radioactive phosphatidylethanolamines appearing in the plasma was approximately ten times lower than that for phosphatidylcholines. No selectivity was observed in the transfer into plasma of different molecular species of phosphatidylethanolamine.

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