Covalently bound fatty acids in the gastrointestinal epithelial cell membrane.

Myristic, palmitic, stearic, oleic and linoleic acids have been identified as the covalently bound fatty acids in the monkey gastrointestinal mucosal membrane proteins and among them palmitolation was predominant. Distribution studies in various regions of the gastrointestinal mucosa showed no significant difference in the content and composition of covalently bound fatty acids in these membrane and most of the fatty acids were found to be ester linked. Total membranes from isolated crypt and villus enterocytes and colonocytes had similar composition of these fatty acids. Covalently bound fatty acid levels were higher in the small intestinal brush border membrane. As suggested for the mucus glycoproteins, covalently bound fatty acids in the intestinal epithelial cell membrane may protect these membranes from proteolytic damage from the luminal proteases.     

Effects of a low dietary linoleic acid level on intestinal morphology and enterocyte brush border membrane lipid composition.

The influence of low dietary linoleic acid level (an essential fatty acid deficiency) on the intestine mucosal morphology and the purified brush border membrane (BBM) lipid composition was investigated in the rat. Electron micrographs and morphometric measurements showed that villi and crypt sizes as well as the ultrastructure of epithelial cells were altered. Cholesterol (CHOL) and phospholipid (PL) levels, CHOL/PL ratio and PL class distribution were not changed by the low linoleate diet. However, the fatty acid composition of phospholipids was markedly modified in the enterocyte BBM, showing elevated amounts of palmitoleic (16:1n-7), oleic (18:1n-9) and 5,8,11-eicosatrienoic (20:3n-9) acids and, by contrast, depressed linoleic (18:2n-6) and arachidonic (20:4n-6) acid levels. Although the underlying mechanisms remain unknown the results obtained suggest that essential fatty acids (EFA) could be directly involved in the trigger action of the observed alterations, as regards both their dynamic (metabolic) and structural roles.     

Influence of dietary partially hydrogenated fat high in trans fatty acids on lipid composition and function of intestinal brush border membrane in rats

The effect of dietary hydrogenated fat (Indian vanaspati) high in trans fatty acids (6 en%) on lipid composition, fluidity and function of rat intestinal brush border membrane was studied at 2 and 8 en% of linoleic acid. Three groups of weanling rats were fed rice-pulse based diet containing 10% fat over a ten week period: Group I (groundnut oil), Group II (vanaspati), Group III (vanaspati + safflower oil). The functionality of the brush border membrane was assessed by the activity of membrane bound enzymes and transport of D-glucose and L-leucine. The levels of total cholesterol and phospholipids were similar in all groups. The data on fatty acid composition of membrane phospholipids showed that, at 2 en% of linoleic acid in the diet, trans fatty acids lowered arachidonic acid and increased linoleic acid contents indicating altered polyunsaturated fatty acid metabolism. Alkaline phosphatase activity was increased while the activities of sucrase, gamma-glutamyl transpeptidase and transport of D-glucose and L-leucine were not altered by dietary trans fatty acids. However at higher intake of linoleic acid in the diet, trans fatty acids have no effect on polyunsaturated fatty acid composition and alkaline phosphatase activity of intestinal brush border membrane. These data suggest that feeding dietary fat high in trans fatty acids is associated with alteration in intestinal brush border membrane polyunsaturated fatty acid composition and alkaline phosphatase activity only when the dietary linoleic acid is low.     

The mucosa of the small intestine: development of the cellular lipid composition during enterocyte differentiation and postnatal maturation

Alterations in lipids linked to intestinal maturation and enterocyte differentiation were reviewed. The 3 main lipid components of cell membranes, ie cholesterol, phospholipids and glycolipids, were examined. Cell phospholipid content increases from the crypts to the mid-villus, which accounts for membrane development and organelle growth in differentiating cells. Changes in the proportion of phospholipid polar head groups occur in brush border membrane during postnatal maturation of the small intestine. The possibility that phospholipid fatty acid composition in differentiating cells might be altered by dietary lipids is discussed. Cholesterol biosynthesis mainly occurs in crypt and lower villus cells whereas its absorption from luminal content and esterification into lipoproteins occur in upper villus mature cells. Cholesterol cell content increases in mature cells in comparison to immature cells on the one hand, and in the distal by comparison with proximal parts of the intestine on the other. Increasing cholesterol content is generally correlated with decreasing membrane fluidity, which in turn could modulate functional properties of the mucosa. Glycosphingolipids are mainly found in the brush border membrane, which contains 20-30% glycolipids by weight of total lipids. These components tend to reinforce the membrane stability and significantly contribute to the surface properties of epithelial cells. The latter undergo noticeable changes during cell differentiation and postnatal maturation. Significant changes in both the glycosidic and lipophilic parts of glycosphingolipid molecules occur in differentiating cells and are of possible importance in the process of mucosal maturation. It is possible that the addition of a terminal sialic acid (sialyltransferase activity) instead of a terminal galactose (galactosyltransferase) to an endogenous acceptor (lactosylceramide) could constitute an important event in the differentiation process, and may account for the increasing content of hematosides along the intestinal villus of rat. Alterations in lipid counterpart mainly consist of hydroxylation of fatty acids in hematosides during postnatal maturation or in glucosylceramides during cell differentiation. Collectively these intestinal lipid changes may contribute in part to the development of mucosal barrier, selective permeability and functional properties of the mature intestinal mucosa.     

Alterations in the physical state and composition of brush border membrane lipids of rat enterocytes during differentiation

The physical state of the membrane lipid of brush border membranes, prepared from rat small intestinal villus and crypt cells, was examined by steady-state fluorescence polarization using three lipid-soluble fluorophors. Membranes prepared from crypt cells were found to possess a higher lipid fluidity than those of villus cells with each probe. Analysis of the composition of these membranes revealed that those from crypt cells had lower ratios of cholesterol/phospholipid (mol/mol), protein/lipid (w/w), and saturated fatty acyl chains/unsaturated chains (w/w). Alterations in the levels of stearic (18:0) and oleic (18:1) acids were responsible for differences in the latter ratio. The results, therefore, demonstrate that alterations in the lipid composition and fluidity of brush border membranes of enterocytes occur during the process of differentiation.     

Ether Lipid Composition and Molecular Species Alterations in Carp Brain (Cyprinus carpio L.) During Normoxic Temperature Acclimation

Carp (Cyprinus carpio L.) whole brain was used to investigate the thermal acclimation changes under normoxic conditions of three-subclasses (alkenylacyl-, alkylacyl- and diacyl-subclasses) of choline glycerophospholipids (CGP), ethanolamine glycerophospholipids (EGP) and inositol glycerophospholipids (IGP) as well as their acyl chain profiles and molecular species composition. The alkenylacyl subclass of CGP and IGP and the alkylacyl subclass of CGP and EGP varied significantly during summer (25°C) acclimation compared to winter (5°C). The levels of alkenylacyl and alkylacyl-CGP, alkylacyl-EGP and alkenylacyl-IGP were 17.3-, 3.7-, 3.5- and 1.3-fold higher in the summer, respectively, while the alkenylacyl EGP was moderately lower. The levels of diacyl subclasses from CGP and IGP were considerably lower in the summer to compensate for the higher proportion of alkenylacyl and alkylacyl subclasses. Significant changes of ether phospholipids and the reorganization of the molecular species composition of all lipid subclasses may be associated with the fine tuning of the physical properties of the cellular membranes in carp brain due to temperature acclimation. The overall acyl chain profile of the three subclasses of carp brain phospholipids showed differences in composition depending upon the subclass of the individual phospholipid. Generally, the polyunsaturated fatty acid (PUFA) chain composition increased relative to monounsaturated fatty acid (MUFA) and saturated fatty acids (SFA) during winter acclimation. Docosahexaenoic acid (DHA) was richer in the winter compared to summer. However, no DHA was found in ether-containing species of IGP from either winter or summer, except for 2% in alkylacyl-IGP during the summer. The above observations suggest that the content of ether phospholipids (alkenylacyl and alkylacyl) as well as the reorganization of the molecular species composition of all phospholipids may serve to maintain a functional fluid-crystalline state to preserve the signaling functions in carp brain.     

Apoptosis in the monkey small intestinal epithelium: structural and functional alterations in the mitochondria

Our earlier studies have shown apoptosis in the villus tip cells of the monkey small intestinal epithelium. Because mitochondria have been implicated in the apoptotic process, this study looked at the function and lipid composition of mitochondria isolated from apoptotic villus tip cells and compared it with middle and crypt cells. Decreased MTT reduction and respiratory control ratio, increased swelling and altered mitochondrial enzyme activities were seen in the villus tip cell mitochondria when compared to other cells. The lipid composition of the villus tip mitochondria were different from the other mitochondria. A decrease in phosphatidylethanolamine and phosphatidyl-inositol and an increase in phosphatidic acid was seen in these mitochondria. Fatty acid composition analysis showed more unsaturated fatty acids in the free fatty acid and phospholipid fraction in villus tip cell mitochondria as compared to other cells. These studies suggest that in the monkey small intestinal epithelium, apoptotic process is associated with functional and structural alterations in the mitochondria.     

Distribution and biosynthesis of aminopeptidase N and dipeptidyl aminopeptidase IV in rat small intestine

The regional, cellular and subcellular distribution patterns of aminopeptidase N and dipeptidyl aminopeptidase IV were examined in rat small intestine. Aminopeptidase N of brush border membrane had maximal activity in the upper and middle intestine, while dipeptidyl aminopeptidase IV had a more uniform distribution profile with relatively high activity in the ileum. Along the villus and crypt cell gradient, the activity of both enzymes was maximally expressed in the mid-villus cells. However there was substantial dipeptidyl aminopeptidase IV activity in the crypt cells. Both enzymes were primarily associated with brush border membranes in all segments, however, in the proximal intestine, a significant amount of dipeptidyl aminopeptidase IV activity was associated with the cytosol fraction. The cytosol and brush border membrane forms of dipeptidyl aminopeptidase IV were immunologically identical and had the same electrophoretic mobility on disc gels. In contrast, the soluble and brush border membrane-bound forms of aminopeptidase N were immunologically distinct. When the total amount of aminopeptidase N and dipeptidyl aminopeptidase IV was determined by competitive radioimmunoassay, there were no regional or cellular differences in specific activity (enzyme activity/mg of enzyme protein) of either enzyme in brush border membrane and homogenate. The specific activity of both enzymes in a purified Golgi membrane fraction as measured by radioimmunoassay was about half that of the brush border membrane fraction. These results suggest that (1) aminopeptidase N and dipeptidyl aminopeptidase IV have different regional, cellular and subcellular distribution patterns; (2) there are enzymatically inactive forms of both enzymes present in a constant proportion to active molecules and that (3) a two-fold activation of precursor enzyme forms occurs during transfer from the Golgi membranes to the brush border membranes.     

Protein turnover in intestinal mucosal villus and crypt brush border membranes

Relative turnover rates of intestinal brush border proteins have been studied by double labelled technique. Brush borders were isolated from cells at all levels along the villus, and from the crypts. Proteins with large molecular weight (>150,000) demonstrated more rapid turnover compared with other brush border proteins at all levels along the villus. This rapid turnover was not seen in crypt brush borders. These findings support the concept of protein turnover in intestinal brush borders, and demonstrate differences between the proteins in rapidly growing crypt cells and non growing villus cells.     

Light microscopic immunocytochemical localization of hepatic and intestinal types of fatty acid-binding proteins in rat small intestine

Monospecific antisera to purified hepatic fatty acid-binding protein (hFABP) and gut fatty acid-binding protein (gFABP) have been used to localize these two proteins in the small intestine of fed rats at the light microscopic level. Pieces of duodenum, jejunum, and ileum were removed from 4-, 10-, 20-, 22-, and 60-day-old Sprague-Dawley rats. Both cryostat and paraffin sections were studied for the presence of hFABP or gFABP by the avidin-biotin immunoperoxidase method. Slides were graded blind for the intensity of staining. Despite the structural and immunological differences between these two proteins, we showed no major differences between their staining patterns or their staining intensity throughout the intestine during postnatal development. The staining for both fatty acid-binding proteins was cytoplasmic. No brush border staining was found. Staining was more intense in the proximal rather than distal intestine, in the villus rather than crypt cells, and in the apex rather than the base of intestinal cells. Shifts in staining patterns, and staining intensity occurring during development may be related to variations in dietary fat intake, rates of cell proliferation, intestinal anatomy, and mechanisms for fat absorption.     

Characterization of isolated villus and crypt cells from the small intestine of the adult mouse

Summary Suspensions of sequentially isolated villus and crypt cells were obtained in order to study certain biochemical changes associated with differentiation of epithelial cells in the small intestine of the mouse. Microscopic observation of the various cell fractions reveals that the epithelial cells detach as individual cells or small sheets of epithelium from the tip to the base of the villus, whereas cells in the crypt regions are separated as entire crypt units. The isolated cells retain their ultrastructural integrity as judged by electron microscopy. Chemical characterization of the various fractions shows that the total cellular protein content, expressed in activity per cell, remains relatively constant throughout the villus region followed by a noticeable drop in the crypt zone. On the other hand, sharp variations in values of cell DNA content are observed in the crypt zone depending on the reference of activity being used. Activity profiles of several brush border enzymes confirm the biochemical changes that occur during the migration of cells from the crypt to the villus tip, as observed in other species, with maximum activity of sucrase in the mid-villus region, of glucoamylase, trehalase, lactase and maltase in the upper third region, and of alkaline phosphatase at the villus tip. Forty-eight-hour suspension cultures of cell fractions corresponding to cells at the base of the villus and crypt zones show a moderate decrease in protein and enzyme activities to approximately 70% of their original value, with DNA content remaining stable throughout the incubation period. The use of biochemical activities as indicators of cellular integrity during cell culture is discussed.Supported by a research grant from the Medical Research Council of Canada (J.H.)     

Mechanism of inhibition of proton: Dipeptide co-transport during chronic enteritis in the mammalian small intestine

Amino acids, a critical energy source for the intestinal epithelial cells, are more efficiently assimilated in the normal intestine via peptide co-transporters such as proton:dipeptide co-transport (such as PepT1). Active uptake of a non-hydrolyzable dipeptide (glycosarcosine) was used as a substrate and PepT1 was found to be present in normal villus, but not crypt cells. The mRNA for this transporter was also found in villus, but not crypt cells from the normal rabbit intestine. PepT1 was significantly reduced in villus cells also diminished in villus cell brush border membrane vesicles both from the chronically inflamed intestine. Kinetic studies demonstrated that the mechanism of inhibition of PepT1 during chronic enteritis was secondary to a decrease in the affinity of the co-transporter for the dipeptide without an alteration in the maximal rate of uptake (V_max). Northern blot studies also demonstrated unaltered steady state mRNA levels of this transporter in the chronically inflamed intestine. Proton dipeptide transport is found in normal intestinal villus cells and is inhibited during chronic intestinal inflammation. The mechanism of inhibition is secondary to altered affinity of the co-transporter for the dipeptide.     

Relative acylglycerol acyltransferase activities in homogenates of enzymically dispersed rat jejunal villus and crypt cells

The relative acyltransferase activities were compared in homogenates of rat jejunal villus and crypt cells isolated by differential scraping and hyaluronidase dispersion. The contributions of the monoacylglycerol and phosphatidic acid pathways to the higher acylglycerol and phospholipid biosynthesis were assessed using 2-oleoyl-sn-[3H] glycerol and [I-14C] palmitic acid as tracers. The stereochemical course of the diacylglycerol biosynthesis was determined by stereospecific analysis. Using 2-oleoyl-sn-glycerol as a tracer, the villus cells exhibited for times higher diacylglycerol and 19 times higher triacylglycerol biosynthesis than crypt cells on an equivalent protein basis. Furthermore, while the villus cell homogenates yielded a preponderance (75%) of the 1, 2-diacyl-sn-glycerols, the crypt cell homogenates formed essentially racemic proportions of 1, 2- and 2,3-diacyl-sn-glycerols. Both villus and crypt cell homogenates exhibited comparable acyl acceptor and acyl donor concentration dependence and the same cofactor requirements. It is unlikely that these acyltransferase activities in the crypt cell preparation are due to contamination with the villus cells, because then more comparable proportions of the enantiomeric diacylglycerols and triacylglycerols would have been anticipated. It is concluded that the crypt cells possess intrinsic monoacylglycerol and to a much lesser extent diacylglycerol acyltransferase activities, which are acquired prior to the development of a distinct brush border and which probably do not require dietary stimulus for induction.     

Fatty acid composition in native and cultured human endothelial cells

Endothelial cells from human umbilical veins were isolated by collagenase treatment. Cells were cultured in the presence of either 20% fetal bovine serum (FBS) or 20% human serum (HS). At confluency, endothelial cell lipids were labeled with tracer concentrations of tritiated arachidonic acid, then extracted and separated into lipid subclasses by thin layer chromatography. The fatty acid composition of each lipid class was determined by glass capillary gas-liquid chromatography analysis and compared to that of cells freshly isolated from the cord (NC cells). The fatty acid compositions differed only in phospholipids. Polyunsaturated fatty acids (PFAs), arachidonic, and linoleic acids were depleted in FBS cell phospholipids and replaced by both stearic and oleic acids. No significant difference could be observed between NC cell and HS cell phospholipids. We conclude that PFAs might be decreased in FBS cells because of the relative paucity of PFAs in FBS as compared to HS. It seems therefore more convenient to cultivate endothelial cells in the presence of HS, especially in respect to their phospholipid content of arachidonic acid, which is the physiological reservoir for prostacyclin synthesis.     

Differential turnover of phospholipid acyl groups in mouse peritoneal macrophages

Phospholipid acyl turnover was assessed in mouse peritoneal exudate cells which consisted primarily of macrophages. The cells were incubated for up to 5 h in media containing 40% H218O, and uptake of 18O into ester carbonyls of phospholipids was determined by gas chromatography-mass spectrometry of hydrogenated methyl esters. The uptake was highest in choline phospholipids and phosphatidylinositol, less in ethanolamine phospholipids, and much less in phosphatidylserine. Acyl groups at the sn-1 and sn-2 positions of diacyl glycerophospholipids, including arachidonic and other long-chain polyunsaturated fatty acids, acquired 18O at about the same rate. Acyl groups of alkylacyl glycerophosphocholine exhibited lower rates of 18O uptake, and acyl groups of ethanolamine plasmalogens (alkenylacyl glycerophosphoethanolamines) acquired only minimal amounts of 18O within 5 h, indicating a low average acyl turnover via free fatty acids. Pulse experiments with exogenous 3H-labeled arachidonic acid supported the concept that acylation of alkenyl glycerophosphoethanolamine occurs by acyl transfer from other phospholipids rather than via free fatty acids and acyl-CoA. The 18O content of intracellular free fatty acids increased gradually over a 5-h period, whereas in extracellular free fatty acids it reached maximal 18O levels within the first hour. Arachidonate and other long-chain polyunsaturated fatty acids were found to participate readily in deacylation-reacylation reactions but were present only in trace amounts in the free fatty acid pools inside and outside the cells. We conclude that acyl turnover of macrophage phospholipids through hydrolysis and reacylation is rapid but tightly controlled so that appreciable concentrations of free arachidonic acid do not occur.     

Manipulation of fatty acid composition of membrane phospholipid and its effects on cell growth in mouse LM cells

Fatty acid composition of the phospholipids of mouse LM cells grown in suspension culture in serum-free chemically defined medium was modified by supplementing the medium with various fatty acids bound to bovine serum albumin.Following supplementation with saturated fatty acids of longer than 15 carbons (100 μM) profound inhibition of cell growth occurred; this inhibitory effect was completely abolished when unsaturated fatty acids were added at the same concentration. Supplementing with unsaturated fatty acids such as linoleic acid, linolenic acid or arachidonic acid had no effect on the cell growth.Fatty acid composition of membrane phospholipids could be manipulated by addition of different fatty acids. The normal percentage of unsaturated fatty acids in LM cell membrane phospholipids (63%) was reduced to 35–41% following incorporation of saturated fatty acids longer than 15 carbon atoms and increased to 72–82% after addition of unsaturated fatty acids.A good correlation was found between the unsaturated fatty acid content of membrane phospholipids and cell growth. When incorporated saturated fatty acids reduced the percentage of unsaturated fatty acids in membrane phospholipids to less than 50%, severe inhibition of the cell growth was found. Simultaneous addition of an unsaturated fatty acid completely abolished this effect of saturated fatty acids.     

Intestinal calcium-binding protein

Summary The vitamin D-dependent calcium-binding protein (CaBP) was studied in relation to the age of the cell, in isolated epithelial cell populations removed from rat duodenum. Alkaline phosphatase and thymidine kinase activities were used as markers to characterize differentiated villus cells and undifferentiated (mitotically active) crypt cells, respectively. CaBP distribution along the length of the villus, as established by radioimmunoassay, appears as a gradient increasing from the crypt to the tip of the villus. CaBP concentration in cells is shown to be (i) negatively correlated with the thymidine kinase activity of cells, and (ii) positively correlated with the alkaline phosphatase activity of cells. This indicates that CaBP is absent in crypt cells and appears in differentiated cells with the development of the brush border. Thus CaBP, like alkaline phosphatase, can be considered as an indicator of enterocyte maturation. These data were also confirmed by studying the cellular localization of the protein. In addition both indirect immunofluorescence and immunoperoxidase staining methods reveal that antibody against CaBP decorates the terminal web, but not the microvilli of the brush border of mature absorptive cells. The results suggest that CaBP may act as a modulator of some Ca²⁺-mediated biochemical processes at the level of the enterocyte brush border.Portions of this work were presented at the Fourth International Workshop on Calcified Tissues, Israel (March 1980)     

THE FATTY ACID COMPOSITION OF PHOSPHOLIPIDS AND GLYCOLIPIDS IN JIMPY MOUSE BRAIN

Abstract— Phospholipids and sphingolipids from brains of normal and Jimpy mice were isolated in a pure form by thin-layer chromatographic procedures. The fatty acid composition of the major phospholipids, i.e. ethanolamine glycerophospholipids, serine glycerophospholipids, choline glycerophospholipids and inositol glycerophospholipids, as well as sphingomyelin, cerebrosides and sulphatides was determined by gas-liquid chromatography. A specific fatty acid pattern for each of the four glycerophospholipids was found. The fatty acid composition of inositol glycerophospholipid, which has not previously been studied in mouse brain, was characterized by a high concentration of arachidonic acid. After 16 days of age, fatty acid analysis showed definite differences between the phospholipids from normal and mutant brains. A small increase of polyunsaturated fatty acids in glycerophospholipids of ethanolamine, serine and choline from the Jimpy central nervous system was found, which has been explained by the myelin deficiency. Sphingomyelin, cerebrosides and sulphatide analyses showed a wide distribution of saturated and mono-unsaturated fatty acids in both normal and mutant mice. A reduction in the amount of long-chain fatty acids was demonstrated in mutant brain sphingolipids; in sulphatides and cerebrosides, the amount of non-hydroxy fatty acids was reduced to a greater extent than in sphingomyelin. The distribution of fatty acids in sphingolipids from the myelin and microsomal fractions was also investigated in both types of mice. Cerebrosides were characterized by a high content of long-chain fatty acids in myelin as well as in microsomes. Sulphatides and sphingomyelin, on the other hand, showed a higher content of medium-chain fatty acids in microsomes than in myelin. In the mutant brain, the amount of long-chain fatty acids was reduced in both subcellular fractions. The deviation from normal in the pattern of fatty acid distribution in Jimpy brain is discussed in relation to the current concepts of glycolipid biosynthesis.     

Effect of dietary supplementation with a fish oil concentrate on the alkenylacyl class of ethanolamine phospholipid in human platelets

It has been demonstrated that the alkenylacyl class of ethanolamine phospholipid (PE) represents one of the major forms of eicosapentaenoic acid (EPA)-containing phospholipid in the circulating platelets isolated from human subjects consuming a fish oil concentrate. Since the alkenylacyl PE from human platelets is enriched in the eicosanoid precursor arachidonic acid (AA) and the n-6 polyunsaturate adrenic acid (AdA), it was of interest to study changes in alkenylacyl PE fatty acid composition upon fish oil supplementation. Healthy volunteers were given 20 capsules of MaxEPA daily (3.6 g of EPA plus 2.4 g of docosahexaenoic acid, DHA) for 6 weeks followed by a 6-week recovery period. Washed platelet suspensions were prepared and the fatty acid compositions of the phospholipid components were evaluated by thin-layer and gas-liquid chromatography at weeks 0, 3, 6, 9, and 12. Fatty acid composition changes were more pronounced in the alkenylacyl PE than in other platelet phospholipids as a result of fish oil consumption. The alkenylacyl PE exhibited a greater drop (by 20.3 mol%, i.e., from 72.0 to 51.7 mol%) in AA than diacyl PE (by 1.6 mol%) or total (predominantly diacyl) choline phospholipids (PC) (by 4.5 mol%). In alkenylacyl PE, the predominant reservoir of AdA in human platelet phospholipid, a dramatic reduction in the level of AdA also resulted with MaxEPA supplementation (from 7.9 to 3.1 mol%); diacyl PE and total PC decreased by 0.6 and 0.3 mol%, respectively. With respect to the n-3 fatty acids, EPA rose by 12.5 mol% in alkenylacyl PE, compared to only 3.8 and 2.5 mol% in diacyl PE and total PC, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)