Choline Phosphoglycerides Research Articles

AD 6(8-monochloro-3-beta-diethylamino-ethyl-4-methyl-7-ethoxycarbonyl-methoxy coumarin) Inhibits the release of arachidonic acid in human platelets stimulated by thrombin

The coumarin derivative AD 6 is known to inhibit platelet aggregation and release and it possesses vasodilatory properties on coronary arteries of laboratory animals. Furthermore, the inhibition of the production of TxB 2 from endogenous substrates after stimulation of human platelets with collagen has been demonstrated. The present report demonstrates that AD 6 inhibits the production of labeled arachidonic acid and diglycerides from phospholipids of platelets stimulated with thrombin. This effect is dose-dependent and is already evident at a concentration of the drug (25μM) which is unable to prevent the aggregation. Apparently, AD 6 inhibits the release of arachidonic acid from phosphatidylinositol and choline phosphoglycerides which are the main sources of the substrate for the synthesis of prostaglandins and thromboxanes.

The thrombin-dependent enrichment of alkenylacyl ethanolamine phosphoglyceride with [14C]eicosapentaenoic and [3H]arachidonic acids in prelabelled human platelets.

The thrombin-dependent enrichment of alkenylacyl ethanolamine phosphoglyceride in [14C]eicosapentaenoic acid [( 14C]EPA) was demonstrated and compared with [3H]arachidonic acid [( 3H]AA) following the simultaneous prelabelling of individual human platelet phospholipids with these two fatty acids. The alkenylacyl, diacyl, and alkylacyl classes of ethanolamine phosphoglycerides (PE) were separated by thin-layer chromatography as their acetylated derivatives after hydrolysis of the parent phospholipid with phospholipase C. The ratios of [3H]/[14C] for the increased radioactivity appearing in alkenylacyl PE following 60 and 120 s of thrombin stimulation were the same as the corresponding ratio (2.0) found in the choline phosphoglycerides (PC) from control (unstimulated) platelets. These results suggest no significant selectivity between EPA and AA in the thrombin-stimulated transfer of these fatty acids from diacyl PC to alkenylacyl PE. The present findings may possibly bear some relevance to the altered platelet reactivity and (or) decreased thromboxane A2 formation observed in human subjects following the ingestion of marine lipid containing EPA.

Effects of parenteral nutrition with high doses of linoleate on the developing human liver and brain

The developmental changes in the fatty acid composition of ethanolamine phosphoglycerides (EPG) and choline phosphoglycerides (CPG) were studied in the liver and brain of 18 newborn infants with gestational ages ranging from 20 to 44 wk. A small group of five newborns receiving total parenteral nutrition (TPN) with high doses of linoleic acid (18:2 omega 6) was also studied and compared to controls of the same gestational age to look for effects on the developmental fatty acid patterns of liver and brain EPG and CPG. TPN with Intralipid 20% was given for 4-12 days, the total fat intake being 14.7-90 g (mean +/- S.D. = 47.1 +/- 29.8 g). The main developmental changes in the liver and brain of the control group were an increase in 22:6 omega 3 (docosahexaenoic acid) at the end of gestation and a linear decrease in 20:4 omega 6 (arachidonic acid) and 18:1 omega 9 (oleic acid) in EPG and CPG. A very good correlation in the percent values of these fatty acids in the brain and liver tissues was obtained. Very significant changes in the fatty acid composition of liver EPG and CPG could be found in the infants receiving TPN with Intralipid-mainly an increase in 18:2 omega 6, a decrease in the linoleate elongation/desaturation to longer members of the series and a decrease in the 22:6 omega 3 levels of liver EPG and CPG. In the brain, only an increase in the 18:2 omega 6 value of CPG, not accompanied by any increase in the longer omega 6 fatty acids, could be detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Docosahexaenoic acid metabolism and effect on prostacyclin production in endothelial cells

Bovine aortic endothelial cultures readily take up docosahexaenoic acid (DHA). Most of the DHA was incorporated into phospholipids, primarily in ethanolamine and choline phosphoglycerides, and plasmalogens accounted for 34% of the DHA contained in the ethanolamine fraction after a 24-h incubation. The retention of DHA in endothelial phospholipids was not greater than other polyunsaturated fatty acids and unlike arachidonic and eicosapentaenoic acids, DHA did not continue to accumulate in the ethanolamine phosphoglycerides after the initial incorporation. About 15% of the [ 14C(U)]DHA uptake was retroconverted to docosapentaenoic and eicosapentaenoic acids in 24 h. Some of the newly incorporated [ 14C(U)]DHA was released when the cells were incubated subsequently in a medium containing serum and albumin. The released radioactivity was in the form of free fatty acid and phospholipids and after 24 h, 11% was retroconverted to docosapentaenoic and eicosapentaenoic acids. Total DHA uptake was decreased only 10% by the presence of a 100 μ m mixture of physiologic fatty acids, but as little as 10 μ m docosatetraenoic acid reduced DHA incorporation into phospholipids by 25%. DHA was not converted to prostaglandins or lipoxygenase products by the endothelial cultures. When DHA was available, however, less arachidonic acid was incorporated into endothelial phospholipids, and less was converted to prostacyclin (PGI 2). Enrichment of the endothelial cells with DHA also reduced their capacity to subsequently produce PGI 2. These findings indicate that endothelial cells can play a role in DHA metabolism and like eicosapentaenoic acid, DHA can inhibit endothelial PGI 2 production when it is available in elevated amounts.

Eicosapentaenoic acid utilization by bovine aortic endothelial cells: effects on prostacyclin production

We have investigated whether the presence of other fatty acids in physiologic amounts will influence the effects of eicosapentaenoic acid on cellular lipid metabolism and prostaglandin production. Eicosapentaenoic acid uptake by cultured bovine aortic endothelial cells was time and concentration dependent. At concentrations between 1 and 25 μM, most of the eicosapentaenoic acid was incorporated into phospholipids and of this, 60–90% was present in choline phosphoglycerides. Eicosapentaenoic acid inhibited arachidonic acid uptake and conversion to prostacyclin (prostaglandin I 2) but was not itself converted to eicosanoids. Only small effects on the uptake of 10 μM eicosapentaenoic acid occurred when palmitic, stearic or oleic acids were added to the medium in concentrations up to 75 μM. In contrast, eicosapentaenoic acid uptake was reduced considerably by the presence of linoleic, n-6 eicosatrienoic, arachidonic or docosahexaenoic acids. Although a 100 μM mixture of palmitic, stearic, oleic and linoleic acid (25:10:50:15) had little effect on the uptake of 10 or 20 μM eicosapentaenoic acid, less of this acid was channeled into endothelial phospholipids. However, the fatty acid mixture did not prevent the inhibitory effect of eicosapentaenoic acid on prostaglandin I 2 formation in response to either arachidonic acid or ionophore A23187. An 8 h exposure to eicosapentaenoic acid was required for the inhibition to become appreciable and, after 16 h, prostaglandin I 2 production was reduced by as much as 60%. These findings indicate that the capacity of aortic endothelial cells to produce prostaglandin I 2 is decreased by continuous exposure to eicosapentaenoic acid. Even if the eicosapentaenoic acid is present as a small percentage of a physiologic fatty acid mixture, it is still readily incorporated into endothelial phospholipids and retains its inhibitory effect against endothelial prostaglandin I 2 formation. Therefore, these actions may be representative of the in vivo effects of eicosapentaenoic acid on the endothelium.

Lipid composition of alveolar macrophage plasma membrane during postnatal development.

Abstract This study was undertaken to define the age-related alterations in lipid composition that resident rabbit alveolar macrophages (AM) undergo during postnatal development. The eventual goal is to correlate these changes with the functional maturation of these cells. The number of AM recorded from total lung lavages rose markedly during the first 14 days of life, from 4.9 X 10(5) to 1.1 X 10(7). Adult lungs yielded 1.1 X 10(8) AM. A gradual but significant increase in fluorescence polarization (P) was observed during development when purified AM plasma membranes were tagged with the probe 1,6-diphenyl-1,3,5 hexatriene trimethyl ammonium. The rise ranged from a mean P value of less than or equal to 0.22 to 0.24 (p less than 0.001) for AM plasma membranes from rabbits 1- or 7-day-old to 30- or 150-day-old rabbits, respectively. This finding suggests that the fluidity of the AM plasma membrane decreased during postnatal development. Palmitic, stearic, oleic, and linoleic acids were the most prevalent fatty acids found in the neutral lipid fraction of the AM plasma membrane throughout development. The content of stearic acid rose from 10 to 16%, arachidonic acid rose from 2.8 to 9%, myristic acid decreased from 3.2 to 1.3%, palmitic acid decreased from 42 to 36%, and oleic and linoleic acids changed relatively little during the first 30 days of life. The levels of docosatetraenoic and docosapentaenoic increased gradually during the first 14 days of life, and by 30 days of life the levels declined to that observed at birth. The sum of these changes resulted in an increase in the ratio of unsaturated to saturated fatty acids (1 to 1.15) in the neutral lipid fraction. During the first month of life, the neutral lipid fatty acid pool in the total lipid fraction of AM plasma membrane increased from 12 to 18 mole %, cholesterol increased from 7 to 14 mole %, and total phospholipids decreased from 81 to 67 mole %. These changes resulted in increasing the cholesterol to phospholipid ratio from 0.09 at birth to 0.23 by 150 days of life. The levels of all three major lipid fractions were comparable at 30 days and 150 days of life. Adult levels of choline phosphoglycerides, the predominant phospholipid, were observed by 7 days of life to have decreased from 47 to 34.5 mole %, and the levels of ethanolamine phosphoglycerides and sphingomyelin increased from 17.5 to 25 mole % and from 9 to 13 mole %, respectively. Adult levels of lyso-bis-phosphatidic acid were reached by 30 days of life increasing from 8.2 to 17.8 mole %.(ABSTRACT TRUNCATED AT 400 WORDS)

The distribution and acyl composition of plasmalogens in guinea pig heart.

In guinea pig heart homogenate, 34% of both choline and ethanolamine phosphoglycerides were in the form of plasmalogens (1-alkenyl, 2-acyl glycerophospholipid). Plasmalogens accounted for 39% of the choline phosphoglycerides and 36% of the ethanolamine phosphoglycerides in the mitochondrial fraction. Ethanolamine plasmalogen was the major ethanolamine phosphoglyceride (63%) in the guinea pig heart microsomal fraction. A high arachidonyl content was found in both diacyl and 1-alkenyl, 2-acyl glycerophosphoethanolamine. The C-2 fatty acyl profiles of the diacyl and 1-alkenyl, 2-acyl choline phosphoglycerides differed considerably from each other in the homogenate as well as in the subcellular fractions. Significant differences in the C-2 fatty acyl profiles also were observed in diacyl and 1-alkenyl, 2-acyl ethanolamine phosphoglycerides. Such differences suggest there is no direct metabolic relationship between the diacyl glycerophosphocholine (-ethanolamine) and its plasmalogen analog.

Phospholipid fatty acid composition and cold tolerance in two species of barnacle, Balanus balanoides (L.) and Elminius modestus Darwin. I. Summer versus winter variations in phospholipid fatty acid composition of whole animals

Total phospholipids, choline phosphoglycerides, ethanolamine phosphoglycerides, phosphatidyl-serine + phosphatidylinositol, and sphingomyelin were isolated in winter and summer from whole bodies of the intertidal barnacles, Balanus balanoides (L.) and Elminius modestus Darwin. The fatty acid compositions were determined for these fractions for two years. Parallel determinations of cold tolerance indicated that the tolerance of Balanus balanoides to low temperatures increased from summer to winter while that of Elminius modestus remained unchanged. Fractions from both species showed seasonal changes in fatty acid composition but those which were consistent between years and which differed between species were confined to sphingomyelin. In E. modestus these changes involved a winter to summer increase in monounsaturated fatty acid levels met by a decrease in the level of saturated fatty acids. The trend for Balanus balanoides was similar but less marked. Sphingomyelin was also characteristic in having a low level of polyunsaturated fatty acids, in contrast with other phospholipid fractions examined. It is suggested that seasonal changes in the fatty acid composition of sphingomyelin, a phospholipid which is located primarily in the plasma membrane, may play some as yet undetermined rôle in the avoidance of freezing injury resulting from damage to this membrane.

Metabolic disturbances of synaptosomes isolated from ischemic gerbil brain.

The effects of cerebral ischemia, induced for 10 min by bilateral common carotid ligation in the Mongolian gerbil, on the brain and synaptosomal content of phospholipids and free fatty acids were measured. Moreover, the incorporation of arachidonic acid and oleoyl-CoA into phospholipids, as well as the respiration and the accumulation of 45Ca, norepinephrine, dopamine, choline, glutamate, and gamma-aminobutyrate in the ischemic brain synaptosomal fraction were studied. Analyses of lipids showed a drop in phospholipids content with concomitant increase of lysocompounds and free fatty acids in ischemic cerebral cortex. Disturbances in lipid metabolism including rapid phospholipids hydrolysis and changes in the incorporation of arachidonic acid into inositol and choline phosphoglycerides were also shown in the synaptosomal fraction of ischemic brain. The uptake of neurotransmitter substances, expressed as a percent of control value, was reduced 21% for norepinephrine, 40% for dopamine, 20% for choline, 24% for glutamate and 13% for gamma-aminobutyrate in ischemic synaptosomes. There was no significant effect of ischemia on synaptosomal respiration and 45Ca uptake in both control and high potassium media. The inhibition of neurotransmitter uptake in ischemic brain synaptosomes may be caused by the disturbance of fatty acid metabolism.

Development changes occurring in the lipids of ram epididymal spermatozoa plasma membrane.

Ram spermatozoa were obtained from different regions (caput, corpus, and cauda) of the epididymis and their plasma membrane was removed using a nitrogen cavitation treatment (750 psi, 10 min equilibration at 4 degrees C). Membrane was recovered after sucrose gradient centrifugation and identified using 125I-succinylated concanavalin A (125I-succConA) as a surface marker. Based on fluorescein isothiocyanate-succConA (FITC-succConA) labeling and electron microscopy, cavitation removed plasma membrane from the anterior sperm head in the area overlying the acrosome. Cholesterol was the major sterol in plasma membrane, with desmosterol present in sperm entering the epididymis (caput sperm) but negligible in sperm after epididymal transit (cauda sperm). Ethanolamine and choline phosphoglycerides represented 70-80% of membrane phospholipids, with the ethanolamine fraction decreasing relative to choline phosphoglycerides during epididymal transit. The molar ratio of cholesterol to phospholipid increased in the plasma membrane during maturation. The bulk phospholipid-bound fatty acids consisted primarily of palmitoyl acyl groups (16:0) in caput sperm and docosahexaenoyl acyl groups (22:6) in cauda sperm. The choline phosphoglyceride fraction was purified and analyzed. It consisted of a mixture of ether acyl glycero-3-phosphocholine and diacyl phosphoglyceride, with the dominant acyl residue, at all stages of epididymal maturation, being 22:6 throughout epididymal transit. The significance of these findings relative to acquisition of fertilization capacity by sperm during epididymal maturation is discussed.

Metabolism of unique diarachidonoyl and linoleoylarachidonoyl species of ethanolamine and choline phosphoglycerides in rat testes

Selected molecular species of rat testicular 1,2-diradyl- sn-glycero-3-phosphocholines and 1,2-diradyl- sn-glycero-3-phosphoethanolamines were quantitated as their diradylglycerobenzoate derivatives, using a recently developed high-performance liquid Chromatographic method. Increased amounts of docosapentaenoic acid were found in glycerophospholipids containing ether moieties compared with the diacyl phospholipids (e.g., docosapentaenoate-containing species comprised more than 80% of the alkylacyl subclass of the ethanolamine phosholipids as opposed to 29.3% of the diacyl subclass). Within 2 h after intratesticular injections of [5,6,8,9,11,12,14,15- 3H]arachidonic acid, the 20:4–20:4 and 18:2–20:4 molecular species of the diacyl subclass of both the choline and ethanolamine glycerophosphatides had the highest specific radioactivities. These unique molecular species (20:4–20:4 and 18:2–20:4) also exhibited the largest percentage decrease in specific radioactivity 24 h after the intratesticular injections of [ 3H]arachidonic acid, which indicates these two species possess a high metabolic turnover. Two of the arachidonate-containing molecular species (18:1–20:4 and 18:0–20:4) in the ethanolamine plasmalogens showed only a small decrease in specific radioactivity, whereas a third species (16:0–20:4) actually had a 44% increase in specific radioactivity 24 h after the intratesticular injections of [ 3H]arachidonate. These data indicate that the 20:4–20:4, 18:2–20:4 and 18:1–20:4 species of phosphatidylcholine and/or phosphatidylethanolamine are most rapidly labeled after administration of [ 3H]arachidonic acid and that they appear to serve as the source of the [ 3H]arachidonate that is ultimately transferred to ethanolamine plasmalogens.

The utilization of ethanolamine and serine for ethanolamine phosphoglyceride synthesis by human Y79 retinoblastoma cells.

Phospholipid synthesis was investigated in human Y79 retinoblastoma cells, a cultured cell line of retinal origin that retains many neural characteristics. Ethanolamine is taken up by Y79 cells through a high-affinity transport system and is utilized to synthesize ethanolamine and choline phosphoglycerides. High-affinity ethanolamine uptake has a K'm of 40.6 microM and a V'max of 1.06 nmol/min/mg protein, and the process is Na+ dependent. Choline is the only compound tested that reduced ethanolamine uptake, and very high choline concentrations were required to produce this effect. The cells incorporate ethanolamine into phosphatidylethanolamine and ethanolamine plasmalogen at equivalent rates, and the rates of catabolism of these phospholipids are similar. Only a small quantity of ethanolamine is incorporated into phosphatidylcholine, but the amount is not reduced by the addition of choline. Serine is incorporated into phosphatidylserine, which then is converted to phosphatidylethanolamine. Ethanolamine reduces but does not abolish this conversion. Unlike ethanolamine, only a small amount of serine is incorporated into ethanolamine plasmalogen. It is possible that the ethanolamine high-affinity uptake system is necessary to provide a neural cell with enough free ethanolamine for ethanolamine plasmalogen synthesis.

Lipid composition of the plasma membrane isolated from hyperplastic nodules of rat liver.

Hyperplastic nodules and hepatomas were induced in livers of rats fed a diet containing 0.05% N-2-fluorenylacetamide (2-FAA). The lipid contents, and phospholipid and fatty acid compositions were analyzed in plasma membranes (PM's) isolated from these tissues and normal rat liver, and the following trends were observed. The molar ratio of cholesterol to phospholipid-phosphorus (phospholipid-P) increased in the order: hepatoma less than normal liver less than hyperplastic nodules. The molar percentage of plasmalogen to phospholipid-P decreased in the order: hepatoma = hyperplastic nodules greater than normal liver. The percentages of choline phosphoglycerides (sum of phosphatidylcholine and lysophosphatidylcholine) and ethanolamine phosphoglycerides (sum of phosphatidylethanolamine and lysophosphatidylethanolamine) both decreased in the order: hepatoma greater than hyperplastic nodules greater than normal liver. On the other hand, the percentages of sphingomyelin and phosphatidylserine both increased in the order: hepatoma less than hyperplastic nodules less than normal liver. As regards fatty acid composition, the percentages of both 18:1 and 18:2 decreased in the order: hepatoma greater than hyperplastic nodules greater than normal liver. Those of 18:0 and 20:4 increased in the order: hepatoma less than hyperplastic nodules less than normal liver. These results suggested that the lipid bilayer in PM of hyperplastic nodules has characteristics roughly intermediate between those of hepatoma and liver PM's, although the molar ratio of cholesterol to phospholipid-P in hyperplastic nodules PM was not intermediate.

Incorporation and turnover of phospholipid precursors in normal and tumoral glial cells in culture

1. 1. The incorporation and turnover of phospholipid precursors in cultured normal and tumoral glial cells was investigated during the plateau phase of growth. 2. 2. Glycerol was incorporated similarly by all cell types, and was renewed with a half-life of 19–37 hr. 3. 3. Acetate had much longer half-life in primary cultures (50–75 hr) than in proliferative tumor cells (20–40 hr). 4. 4. Phosphate had a more rapid turnover rate in primary cultures (25 hr) than in proliferative tumor cells (50 hr). 5. 5. For all precursors, inositol- and choline phosphoglycerides had a faster turnover rate than other phospholipids.

Studies on ether phospholipids: I. A new method of determination using phospholipase A1 from guinea pig pancreas: Application to krebs ii ascites cells

A new method for ether phospholipid analysis has been devised, based on the selective destruction of diacyl phospholipids by guinea pig phospholipase A 1 and of plasmalogens by acidolysis. The paper describes optimal conditions allowing a specific degradation of diacyl phospholipids by the enzyme(s). This requires the incubation of a total lipid extract in the presence of 2.4 mM sodium deoxycholate, at pH 8.0, at a temperature of 42° C. As shown with various radioactive markers, all the diacyl phospholipids become degraded, whereas sphingomyelin and ether phospholipids remain refractory to phospholipase A 1 attack. Phospholipids are then separated by a bidimensional thin-layer chromatography involving the exposure of the plates to HCl fumes between the two runs, in order to hydrolyse plasmalogens. Selectivity of both hydrolytic procedures is further demonstrated upon analysis of acetyl diacylglycerol derived from phospholipids. Various phospholipids can thus be determined by phosphorus measurement using sphingomyelin as an internal standard. By this way, it is shown that Krebs II cells present a very high content of ether phospholipid species (around 25% of total). Among these, about 50% are alkyl forms in ethanolamine phosphoglycerides, whereas this value reaches 70% in choline phosphoglycerides.

Effects of dietary lipids on behaviour, lipid biosynthesis and lipid composition, in rat platelets

Rats of either sex were fed for 18 and 34 weeks respectively diets containing 40% (by weight) lipids with polyunsaturated fatty acids representing 1.34% or 13.2% of total calories. Platelet reactivity to thrombin, platelet fatty acid composition and incorporation of [ 14C]acetate into platelet lipids were investigated. Diets rich in saturated fatty acids markedly increased platelet sensitivity to thrombin. The concentration of 20:3 and 22:3 of the ( n−9) series and of 20:3 and 22:5 of the ( n−6) series were increased at the expense of 18:2 and 22:4 of the ( n−6) family in platelet lipids. 20:4 ( n−6) was unchanged. The fatty acid changes were more pronounced in male rats and after 34 weeks. [ 14C]Acetate incorporation into total platelet lipids and particularly into choline phosphoglycerides and ceramides was lower in animals fed psaturated fats. This diet reduced the synthesis of 16:0 and of 22:4( n−6) in platelet total fatty acids, while that of 22:3( n−9) was markedly enhanced. This study showed that long-term feeding of high-saturated-low-polyunsaturated fat diets in rats induced marked changes in platelet lipid synthesis and composition, in both sexes. The lipid synthesis modification appears to be more pronounced in males than in females. The changes in the fatty acids 20:3( n−9), 22:3( n−9) and 22:4( n− 6) appeared to be closely related to platelet behaviour. The balance between the content and synthesis of these last fatty acids might be of significance for the effect of diet on thrombogenesis.

Positional Distribution of Acyl and Alk‐1‐enyl Groups in Grey and White Matter Ethanolamine and Choline Phosphoglycerides of a Marsupial, the Koala (Phascolarctos cinereus)

The major phosphoglycerides in grey and white matter from the brain of the koala have been separated and examined. The major polyunsaturated fatty acids present in both the diacyl- and alk-1-enyl acylglycerophosphorylethanolamines from grey matter were 22:6 omega 3, 20:4 omega 6, and 22:4 omega 6. In both grey and white matter, 22:6 omega 3 and 20:4 omega 6 were concentrated in the 2-position of diacylglycerophosphorylethanolamines and 22:4 omega 6 in the 2-position of alk-1-enylacylglycerophosphorylethanolamines; polyunsaturated fatty acid levels were higher in diacylglycerophosphorylethanolamines. Ethanolamine phosphoglyceride fractions from grey matter were enriched in polyunsaturated fatty acids compared with those from white matter. The acyl groups 18:0, 18:1, and 16:0 and their alk-1-enyl analogues were prominent in grey and white matter ethanolamine phosphoglycerides; 18:1 was dominant in white matter alk-1-enylacylglycerophosphorylethanolamines. The plasmalogen composition of ethanolamine phosphoglycerides was 55% in grey matter and 76% in white matter. Choline phosphoglycerides contained negligible plasmalogen and low polyunsaturated fatty acid levels. Diacylglycerophosphorylcholine was characterized by high levels of 16:0 and 18:1. Similar acyl group distributions were estimated in the 1-position in both grey and white matter, 16:0 being present at greater than 50%. The presence of the molecular species 18:0/22:6 omega 3 was indicated in grey matter diacylglycerophosphorylethanolamine, 18:1/18:1 in white matter alk-1-enylcylglycerophosphorylethanolamine, and 16:0/18:1 in white matter diacylglycerophosphorylcholine.

Occurrence of Alkyl Ether Phospholipids in Rabbit Platelets: Compositions and Fatty Chain Profiles

Rabbit platelets contained significant amounts of alkylacyl compounds (10.4%) in choline phosphoglycerides (CPG) and alkenylacyl compounds (46.3%) in ethanolamine phosphoglycerides (EPG). The fatty chain profiles of alkylacyl and diacyl CPG, and alkenylacyl and diacyl EPG were considerably different from each other. Alkylacyl CPG contained higher amounts of 16:0 (35.0%) and 20:4 (20.9%) than diacyl compounds (4.5% and 12.6%, respectively). On the other hand, alkenylacyl EPG included a large amount of 20:4 (58.2%) in comparison with diacyl analogues (28.8%).

Regulation of the composition and positioning of saturated and monoenoic fatty acids in phosphatidylcholine.

The mechanism by which polyenoic acids control the amount and positioning of monounsaturated fatty acids in choline phosphoglycerides from baby hamster kidney cells was studied. Under normal growth conditions monoenoic acids were derived from the desaturation of saturated fatty acids and comprised over 50% of the fatty acids at position 1 of the glycerol moiety. The monoene content of positions 1 and 2 decreased in response to the addition of di- and polyenoic acids to the culture medium. All the di- and polyenoic acid supplements tested inhibited the desaturation of palmitic and stearic acid and replaced monoenes at position 2. However only linoleic, linolenic, and eicosadienoic acids replaced monoenes at position 1. The results suggest that under appropriate conditions up to 25% of the choline phosphoglyceride fraction consisted of a stable molecular species containing di- or trienoic fatty acids at both the 1 and 2 positions of glycerol moiety. With eicosatrienoic or arachidonic acid supplements, on the other hand, the monoenes at position 1 were replaced with saturated fatty acids. The magnitude of these effects, particularly at position 1, was proportional to the concentration of the fatty acid supplement. The results suggest that polyenes with at least 20 carbon atoms can play a key role in determining the ultimate composition and positioning of fatty acids in baby hamster kidney choline phosphoglycerides and that this control is mediated by their ability to inhibit delta 9 desaturase and by a retailoring system specific for these polyenes.

Different fatty chain compositions of alkenylacyl, alkylacyl and diacyl phospholipids in rabbit alveolar macrophages: High amounts of arachidonic acid in ether phospholipids

AbstractHigh levels of ether phospholipids were found in rabbit alveolar macrophages. Choline phosphoglycerides (CPG) contained a significant amount of alkylacyl compound (32.5%). On the other hand, ethanolamine phosphoglyceride (EPG) included a very large amount of alkenylacyl compounds (61.2%). Small amounts of alkenylacyl CPG and alkylacyl EPG were also observed. The occurrence of a high amount of alkylacyl CPG may be related to the synthesis or release of platelet‐activating factor (PAF) from macrophages. Fatty chains at the 1‐ and 2‐positions in each lipid class of CPG or CPG or alkenylacyl EPG were several other. Particularly, the levels of 20∶4 (arachidonic acid) in alkylacyl CPG or alkenylacyl EPG were several times higher than those in corresponding diacyl phospholipids. Large portions of 20∶4‐containing species have alkenyl or alkyl ether moieties at their 1‐position in both CPG (73.6%) and EPG (85.9%). These results suggest the importance of ether‐containing phospholipids in rabbit alveolar macrophages.