Fatty Acid Composition Of Phosphatidylcholine Research Articles

Phospholipid requirement of epididymal testosterone 5α-reductase and phospholipid composition of epididymal microsomes

We have investigated phospholipid requirement for testosterone 5α-reductase solubilized from microsomal and nuclear fractions of rat epididymis. The 5α-reductase from microsomal fraction was stimulated by phosphatidylcholine (PC) with long acyl-chain lengths, but inhibited by short chain PC. The nuclear enzyme activity was weakly activated by PC with various acyl-chain lengths tested. Synthetic phosphatidylserine (PS), such as dioleoylPS, most strongly stimulated the microsomal enzyme activity, but did not exhibit any activation of the nuclear enzyme activity. Endogenous phospholipids, such as PC, PS, and phosphatidylethanolamine (PE) separated from bovine epididymal microsomes were tested for their stimulatory effects on microsomal and nuclear enzymes. Among these endogenous phospholipids, PS most greatly stimulated the microsomal 5α-reductase activity, whereas both PC and PE weakly activated the enzyme activity. On the other hand, endogenous PC and PS had no ability to support the nuclear enzyme activity. The fatty acid compositions of PC and PS from bovine epididymal microsomes were determined, in order to elucidate the relationship between 5α-reductase activation by these phospholipids and the structure of their acyl chains. The relative content of fatty acids in PC, in a decreasing order, was palmitate linolate > oleate; that in PS was stearate > oleate > palmitate. Based on these observations, the roles of microsomal PS and PC in epididymal 5α-reductase reaction will be discussed.

Phospholipid distribution and fatty acid composition of phosphatidylcholine and phosphatidylethanolamine in sperm of some freshwater and marine species of fish

The phospholipid composition and fatty acid characteristics of diacyl and plasmalogen forms of phosphatidylcholine and phosphatidylethanolamine of sperm of five marine and five freshwater species of fish have been determined. There was considerable variation in composition within each group of fish, which obscured any differences which are related to the osmotic environment. Since such factors as temperature, nutrition, etc. probably greatly influence the lipid composition, we failed to determine a relationship between osmolality and phospholipid composition. We have also found certain phospho-lipid peculiarities, characteristic of sperm of various species of fish. Nevertheless, as we have found previously, the molar ratio of cholesterol to phospholipids in fish sperm is determined by the salinity of the habitat.

Interrelationships of bile acid and phospholipid fatty acid species with cholesterol saturation of duodenal bile in health and gallstone disease.

The relative amount of cholesterol and the fatty acid composition of phosphatidylcholines in bile can be influenced by the bile acid species secreted. To search for a contribution of secondary bile acids and of phosphatidylcholines to supersaturation of bile in gallstone disease, we compared the relative amount of cholesterol and the biliary composition of bile acids and of phospholipid fatty acids in cholecystokinin-stimulated duodenal bile of 22 female gallstone patients and 16 healthy controls and analyzed the interrelationships of these bile constituents. Gallstone patients had higher molar percentages of cholesterol than did controls (10.2 +/- 3.2 vs. 6 +/- 1.5 mol%; p less than 0.001) and demonstrated a trend toward larger fractions of deoxycholic and lithocholic acids. By linear models, variation of cholesterol saturation could be predicted (p less than 0.001) up to 53% by the bile acid pattern and up to 81% by the fatty acid pattern of phospholipids. Linear path analysis (goodness-of-fit index = 0.973) confirmed the tight relationship between phospholipid fatty acids (positive: oleic, arachidonic; negative: linoleic, palmitoleic) and the relative amount of cholesterol; more than half the influence of cholic, deoxycholic and lithocholic acids on the relative amount of cholesterol could be explained indirectly by their influence on the phospholipid fatty acid pattern. We conclude that the relationships examined by path analysis support the working hypothesis that secondary bile acids contribute to supersaturation of bile mainly by changing the fatty acid pattern of the secreted phospholipids (presumably the pattern of phosphatidylcholines), which increases the molar ratio of cholesterol/phospholipids in bile.

Metabolic transformation of intracraneally injected [1‐14C]linoleic and [1‐14C]α‐linolenic acids in malnourished developing rats

The effect of a low protein diet during pregnancy and lactation on the fatty acid composition of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) from brains of ten-day-old rats was studied. The results indicated that partial deprivation of protein during early development was associated with an increase in the fatty acids of the n-9 family in PC. The fatty acids of the linoleic acid series decreased in PE but were not modified in PC. These minor changes did not affect the double bond index values either in PC or in PE. The effect of protein depletion on the in vivo metabolic transformation of intracraneally injected [1-14C]linoleic and [1-14C]alpha-linolenic acids was also studied. The percentage distribution of the labeled precursors and their derivatives among PC and PE differed from that of mass distribution. These results indicate that the direct uptake of polyunsaturated fatty acids from the blood and/or the low turnover rate of these acids incorporated into PC and PE might be involved in maintaining the fatty acid pattern of these brain lipids.

Effect of dietary fat on rat liver microsomal and mitochondrial/lysosomal dolichol, phospholipid and cholesterol

The influence of different fat diets on liver phospholipid, cholesterol and dolichol was studied. Rats were separated into four groups and fed standard laboratory chow (control), a diet containing linolenic acid, a coconut oil diet, or a corn oil-containing diet. After five weeks, microsomes and mitochondrial/lysosomal fractions were prepared from the liver, and lipid compositions were analyzed. No changes in phospholipid content were observed. In control animals, the fatty acid compositions of phosphatidylcholine and phosphatidylethanolamine in the two subfractions were similar. However, these two phospholipids showed different fatty acid patterns, which were altered independently upon dietary treatment. The dietary treatments resulted, in most cases, in decreased cholesterol and dolichol contents and, especially in microsomes, in a decreased level of esterification of both lipids. The fatty acid compositions of cholesteryl esters in the two subfractions showed significant differences and cholesterol was esterified to a large extent with linolenic acid when this fatty acid was supplied in the diet. The same dietary treatment exerted different effects on the cholesterol localized in the two different intracellular compartments. This difference was most pronounced in rats fed the corn oil-containing diet; microsomal cholesteryl esters exhibited increased saturation, whereas cholesteryl esters exhibited increased saturation, whereas cholesteryl esters in the mitochondrial/lysosomal fraction displayed decreased saturation. Dolichyl esters in the two cellular compartments had different fatty acyl compositions, with a considerably higher degree of saturation in microsomes. The various diets influenced the nature of the fatty acid moieties present in the isolated fractions and the effects on the two subfractions were opposite.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium-dependent incorporation of choline into phosphatidylcholine (PC) by base-exchange in rat brain membranes occurs preferentially with phospholipid substrates containing docosahexaenoic acid (22 : 6( n—3))

The fatty acid composition of phosphatidylcholine (PC) formed by base-exchange was examined in rat brain membranes in vitro. The free choline incorporated into subspecies of PC by this phospholipase-D type activity can be distinguished from that which might enter indirectly via the last enzyme of the de novo pathway for phospholipid biosynthesis, cholinephosphotransferase, by its ionic requirements. Choline base-exchange in lysed synaptosomes is optimal when assayed at extracellular (mM) calcium concentrations and is blocked by magnesium. As much as 40% of the choline incorporated by base-exchange into rat brain membranes was recovered in subspecies of PC, representing no more than 10% of the total PC pool, which contained docosahexaenoic acid (22:6( n — 3)). Docosahexaenoic acid is enriched in electrically-excitable membranes and its content in phospholipids of rat and human brain change during early development and increase with age.

Dietary protein and fatty acid composition of liver lipids in the rat

In order to compare the effects of different sources of dietary protein on the fatty acid composition of phosphatidylcholines (PC), phosphatidylethanolamines (PE), phosphatidylinositols (PI), cholesteryl esters and triacylglycerols, male rats were fed for a 4-week period on cholesterol-free, or cholesterol-containing, diets based on casein, or soybean protein and olive oil. The most conspicuous difference observed was the occurrence of significantly higher levels of 5,8,11-eicosatrienoic acid, 20:3 ( n−9), in the different lipid classes of casein-fed, compared with soybean protein-fed, animals. In the PI fraction of livers from the groups of rats fed casein diet, this fatty acid amounted to between 9.9 and 13.3% by weight of the total fatty acids. Phospholipids from livers of casein-fed rats contained increased levels of oleic acid, 18:1 ( n−9) (in PC and PE) and reduced levels of stearic acid (18:0). Moreover, in this group of rats PI contained a reduced level of arachidonic acid, 20:4 ( n−6). A casein-related decrease in the linoleic acid, 18:2 ( n−6), content of PC and PE was observed only in the rats fed on cholesterol-free diet. Effects on the fatty acid composition were also observed in the triacylglycerol and cholesteryl ester fractions, in which the rats fed casein diet showed higher levels of palmitoleic acid, 16:1 ( n−7) (cholesterol-supplemented diet) and lower values for linoleic acid, than the soybean protein-fed rats.

Replacement of molecular species of phosphatidylcholine: influence on erythrocyte Na transport

The phosphatidylcholine-specific transfer protein (PC-Tp) from bovine liver was used to replace endogeneous erythrocyte phosphatidylcholine (PC) with various amounts of five different molecular species of PC. Furosemide-sensitive (FS) Rb uptake, Na-Li exchange, and Na-K pump rates were considered in relation to the nature and extent of those replacements. Changes in fatty acid contents of PC after incorporation of different molecular species fell within a variation range (10-30%) similar to that found in large populations of healthy individuals. Di16:0-PC accelerated Na-Li exchange and FS Rb uptake by approximately 40 and 25%, respectively. Some reduction (20%) in FS Rb uptake was seen in 16:0/18:2-PC-enriched erythrocytes. Incorporation of 16:0/22:6-PC accelerated Na-Li exchange and FS Rb uptake by greater than 40 and 20%, respectively. Apart from inhibitory effects of 16:0/18:1-PC and di16:0-PC (24 and 19%, respectively) the Na-K pump rate was virtually unchanged by incorporation of different PC molecular species. Exogeneous PC molecules are exclusively inserted in the outer membrane leaflet and, particularly in the case of di16:0-PC, migrate slowly to the cytoplasmic leaflet. Prolonged incubation of cells (up to 21 h) after replacement with di16:0-PC showed that both Na-Li exchange and FS Rb uptake rates responded differently to redistribution of newly inserted molecules over both bilayer halves. Compared with cells exhibiting a selective incorporation of di16:0-PC in the outer monolayer, additional enrichment with disaturated species in the inner monolayer accelerated FS Rb uptake, whereas Na-Li exchange rate reverted to control values. It is concluded that small changes in fatty acid composition of PC induced by limited replacement of phospholipid molecular species can cause considerable changes in Na-Li exchange rate and FS Rb uptake. Differences in phospholipid molecular species composition could contribute to known interindividual variability of both Na-Li exchange and Na-K cotransport.

Levels of Dihomo-γ-Linolenate are Depressed in Heart Phosphatidylcholine and Phosphatidylethanolamine in the Biotin-Deficient Chick

Male broiler chicks were fed a purified diet with 0 or 500 μg/kg of added biotin for 21 days posthatch. Fatty acid composition of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were determined in erythrocytes and in heart mitochondria and microsomes of chicks at 12 and 21 days of age. The biotin-deficient (BD, 0μg biotin) chicks had lower body weights, lower feed efficiencies, and higher scores for dermatitis and twisted leg than the biotin-adequate (BA, 500 μg biotin) chicks. The erythrocyte arachidonate level in PC was higher in BD chicks compared to the BA controls, and the level increased with age in PC and PE in the erythrocytes. The level of dihomo-γ-linolenate (20:3ω6) in PC and PE in heart mitochondria and microsomes was consistently decreased in BD chicks compared with that in BA chicks. In heart subcellular organelles, the level of arachidonate in PC increased, but the level of dihomo-γ-linolenate in PE decreased with age. These data demonstrate that biotin deficiency results in dramatic changes in the fatty acid composition of specific phospholipids in chick erythrocytes and heart subcellular organelles.

Effect of Dietary Salmon Oil Feeding on Rat Heart Lipid Status

For 2 mo rats were fed a salmon oil diet (12.5%, wt/wt) supplemented with 4.5% (wt/wt) corn oil, a corn oil diet (17%, wt/wt) or a low fat diet (4.4%, wt/wt). Cardiac lipids were analyzed and fatty acid composition of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was determined. Ventricular biopsies were taken for ultramicroscopic examination. Serum cholesterol, triglyceride, phospholipid and vitamin E concentrations were significantly lower in rats fed salmon oil than in those fed the other two diets, whereas serum transaminases and vitamin A were not significantly affected. Cardiac protein, phospholipid, triglyceride and cholesterol concentrations were unaffected by diet. Cardiac phospholipid composition remained unchanged and no significant changes in lyso-PC or lyso-PE levels were observed. However, the salmon oil diet produced a markedly lower n-6/n-3 ratio in both PE and PC than in the other two diets. This was the result of replacement of n-6 polyunsaturated fatty acids (PUFA), primarily 20:4n-6 with n-3 PUFA, primarily 22:6n-3. The unsaturation index of PC and PE was higher with the salmon oil diet than with the other two diets. Ventricular biopsies of rats fed salmon oil showed mild lipid accumulation associated with some lipofuscin-like material. It is suggested that, in rat heart, fish oil led to a moderate accumulation of lipids, the composition of which may include long-chain monounsaturated fatty acids and a degradative form of peroxidized lipids.

Plasma pattern of growth hormone regulates sexual differentiation of phosphatidylcholine in rat plasma.

The effects of continuous and intermittent administration of human growth hormone (hGH) in the regulation of plasma phosphatidylcholine fatty acid composition was studied in adult hypophysectomized male and female Sprague-Dawley rats. Human GH was given for 7 days, either continuously by means of Alzet osmotic minipumps implanted s.c. or intermittently by means of s.c. injections at 12-h intervals. The 'masculinizing' effect of hypophysectomy on the fatty acid composition of plasma phosphatidylcholine in female rats, i.e. an increase in the proportions of palmitic and linoleic acids and a decrease in the proportions of stearic and arachidonic acids, was to a large extent reversed by continuous administration of hGH, while intermittent administration had no consistent effect. This effect of continuous hGH administration similar effect of continuous administration of hGH was also observed in hypophysectomized male rats. Prolactin had no effect on the fatty acid composition of phosphatidylcholine. Replacement therapy with thyroid hormones and glucocorticoids had a small effect on the proportions of palmitic and stearic acids in plasma phosphatidylcholine. It is concluded that the more continuous secretory pattern of GH in female rats is involved in the sexual differentiation of the fatty acid composition of plasma phosphatidylcholine.

Effects of Physiological and Ontogenetical Ageing on Membrane Lipid Levels in Pea Leaves ( Pisum sativum)

Summary The membrane lipid composition of leaves from pea was investigated during different stages of ageing. Total fatty acids, phospholipids, and free sterols were determined, on the one hand, in leaves of different maturity from plants with nine pairs of leaves, on the other hand, in newly unfolded leaves of plants of different ages. The leaves of different maturity were regarded as representing different stages of physiological ageing. The total fatty acids as well as the phospholipids decreased with increasing age. The level of free sterols was, however, constant. This implied a decrease in the mol ratio of free sterols/phospholipids from 0.16 to 0.33. The fatty acid composition of phosphatidylcholine changed to a lower unsaturation degree. The newly unfolded leaves of plants of different ages represented a variation in ontogenetical age with a constant level of physiological maturity. The total acyl lipids and the phospholipids of the newly unfolded leaves varied in a complex way during ontogenetical ageing and showed a min value at a plant size of seven leaves. The free sterols decreased with age. As a consequence the mol ratio of free sterols/phospholipids fluctuated between 0.1-0.2. Taken together the results indicate that the membrane lipid composition of pea leaves changes and reflects that form of ageing which prevails.

Modification of fatty acid composition of membrane phospholipid in hepatocyte monolayer with n − 3, n − 6 and n − 9 fatty acids and its relationship to triacylglycerol production

The objective of these studies with rat hepatocytes in primary culture was to establish that: (a) membrane phospholipids would become enriched with the specific fatty acid supplemented to the media and (b) hepatocyte monolayer triacylglycerol synthetic rates were dependent on the type of fatty acid enrichment of the membrane phospholipids. Hepatocytes cultured in the absence of media lipid developed a phospholipid fatty acid composition which is indicative of an essential fatty acid deficiency. The extensive rise in 18: 1( n − 9) content indicated that Δ 9-desaturase was active. The fatty acid composition of phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol in the microsomal- and mitochondrial-enriched fractions was highly dependent upon the type of fatty acid supplemented to the medium. Incorporation of fatty acids into phospholipids was rapid, and a new steady-state in fatty acid composition was achieved within approx. 36 h. Changes in the fatty acid composition of these hepatocyte phospholipid subclasses resulting from media supplementation with 18:2 20:4 ( n − 6) or 20:5( n − 3) were similar, but not identical, to changes which occurred in vivo as a result of consuming diets rich in 18:2( n − 6) or 20:5( n − 3). Hepatocyte lipogenesis was highly dependent upon the type of fatty acid supplemented to the medium. Prior conditioning with 16:0 increased triacylglycerol synthesis and secretion. Secretion of triacylglycerol was reduced by polyenoic fatty acid enrichment with 20:5( n − 3) > 20:4 18:2 ( n − 6). The suppression of triacylglycerol synthesis by 20:5( n − 3) was due to an increased ( P < 0.05) diacylglycerol specific activity, which indicates that 20:5( n − 3) suppression of hepatic triacylglycerol production may be caused in part by the inhibition of diacylglycerol acyltransferase.

Alteration of hepatic phospholipids in rats and mice by feeding di-(2-ethylhexyl)adipate and di-(2-ethylhexyl)phthalate.

Effects of di-(2-ethylhexyl)adipate (DOA) and di-(2-ethylhexyl)phthalate (DEHP), plasticizers for polyvinylchloride products, on concentrations and compositions of hepatic phospholipids were studied in rats. When administered to rats at a 2% level for 2 wk, both DOA and DEHP caused a hepatomegaly, an increase in hepatic phospholipids and a decrease an increase in hepatic phospholipids and a decrease in the ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE). In the comparable study with mice, the alkyl moiety of DOA was found to be responsible for these alterations. DOA and DEHP specifically altered fatty acid compositions of PC and PE: there was an increase in oleic and palmitic acids and a decrease in stearic and docosahexaenoic acids in PC and an increase in arachidonic acid at the expense of docosahexaenoic acid in PE. In addition, DOA caused an increase in the trienoic and tetraenoic molecular species in PC and an increase in the 1-palmitoyl-2-arachidonyl (16:0@20:4) species in PE. Thus, the effects of DOA on the lipid dynamics resembled those observed with DEHP, although the magnitude was slightly moderated.

Effect of intratracheal instillation of cadmium chloride on phospholipids in alveolar wash fluid

The effect of cadmium chloride on phospholipids in the alveolar wash fluid was investigated by instilling the chemical (2.5 μg Cd/0.4 ml saline per rat) into rat trachea. Two days later the phospholipid content of the was fluid increased markedly in the cadmium-treated group to about 2.4 times that in the control (saline-treated) group. The relative amount of phosphatidylcholine and the fatty acid composition of phosphatidylcholine were not altered by the cadmium treatment, and retained a composition typical of lung surfactant. These findings suggest that cadmium induces a marked increase in surfactant phospholipids in the lung at a very low dose.

Mechanism of arachidonic acid liberation during ischemia in gerbil cerebral cortex.

Once brain ischemia was induced in the gerbil cerebral fronto-parietal cortex, serial changes occurred in energy metabolites and various lipids. The amounts of inositol-containing phospholipids began to decrease immediately after energy failure, followed by an increase in the amount of 1,2-diacylglycerol with a subsequent liberation of arachidonic acid and other free fatty acids. The fatty acid compositions of inositol-containing phospholipids, of 1,2-diacylglycerols produced by ischemia, and of free fatty acids liberated during ischemia were quite similar. The amount of stearic acid liberated was much larger than that of arachidonic acid between 30 s and 1 min of ischemia. On the other hand, there was no significant decrease in the amount of the other phospholipids except for phosphatidic acid. Furthermore, there was also no change in the fatty acid composition of phosphatidylcholine or phosphatidylethanolamine throughout 15 min of ischemia. The amount of cytidine-monophosphate reached a peak (36.7 nmol/g wet wt) at 2 min of ischemia. These results indicated that arachidonic acid was predominantly liberated from inositol-containing phospholipids by phospholipase C, and by the diglyceride lipase and monoglyceride lipase system rather than from phosphatidylcholine or phosphatidylethanolamine by phospholipase A2 or plasmalogenase or choline phosphotransferase during the early period of ischemia.

Effect of di- n-octyl phthalate on fatty acid composition of phosphatidylcholine in Tetrahymena

We examined the effect of di- n-octyl phthalate (DOP) on fatty acid composition of phosphatidylcholine (PC) in Tetrahymena pyriformis NT-1. When Tetrahymena cells were grown in DOP-containing proteose peptone medium, the cell growth was repressed. This repression was attended by decreases in the PC content of the cells and decreases in oleic (18 : 1), linoleic (18 : 2) and linolenic (18 : 3) acids of PC and an increase in palmitoleic acid (16 : 1). The ratio of 18 : 1/stearic acid (18 : 0) of PC in cells grown in DOP-containing medium was lower than that of control cells, while the ratio of 16 : 1/palmitic acid (16 : 0) was higher than that of control. On the other hand, no changes in the ratios of 18 : sol2 18 : 1 and 18 : sol3 18 : 2 were observed. The activity of microsomal stearoyl-CoA desaturase from cells grown with DOP (0.63 μmol/ml medium) decreased to 27% of that from control cells, while the microsomal palmitoyl-CoA desaturase activity increased to 210% of the control value. By the addition of dioleoyl glyceride to the DOP-containing medium, the effects of DOP on Tetrahymena cells were completely blocked. These results suggest that the changes in fatty acid composition of PC may be due to the alteration of the substrate specificity of microsomal Δ 9-desaturase, and the decrease in stearoyl-CoA desaturase activity may be a cause for the cell growth repression.

Effect of Dietary Fat on the Utilization of Fatty Acids by Myocardial Tissue in the Rat

Weanling rats were fed high fat diets containing 40% of energy as fat for 23 d. Diets were formulated to contain equivalent content of essential nutrients per calorie for the nonfat components. Four oil mixtures provided high dietary levels of either oleic, linoleic, linolenic or erucic acid. Effect of dietary fatty acid composition on the fatty acid composition of phosphatidylcholine, phosphatidylethanolamine and cardiolipin isolated from cardiac mitochondria was examined in conjunction with the effect of diet on the oxidative activity of cardiac mitochondria. Dietary treatments that reduced the content of C16:0 in the sn-1 and sn-2 positions of phosphatidylcholine were associated with increased content of C20:1 and C22:1 fatty acids into the sn-2 position and resulted in decreased oxidative activity of cardiac mitochondria utilizing palmitylcarnitine as a substrate for oxidation. Diets high in linoleic acid did not increase membrane phospholipid content of ω3 fatty acids, but resulted in decreased level of C20:4ω6. In a subsequent perfusion experiment, hearts were removed from animals fed either high erucic or high linoleic acid diets and were perfused to examine rates of fatty acid oxidation and simultaneous synthesis of high energy phosphate compounds in cardiac muscle. Diet did not affect the levels of creatine phosphate or adenine nucleotides present in the tissue on a per-gram-wet-weight basis, but production of 14CO2 from β-oxidation of palmitic acid was lower for animals fed the high erucic acid diet than for those fed the high linoleic acid diet. Since this diet did not alter oxidation of palmitylcarnitine in vitro and as β-oxidation of lauric acid was not decreased in the perfused heart, we conclude that mitochondrial oxidation of fatty acid was not altered by diet and that low rates observed for palmitate oxidation are attributable to reduced palmitylcarnitine synthesis.

Lipids and fatty acids in membranes from astroglial cells cultured in ethanol-containing media

A study was undertaken to evaluate the usefulness of a primary brain cell culture for the assessment of general membrane phenomena caused by ethanol. The major aim was to study the inertness versus vulnerability of membrane lipids for 8 days of ethanol exposure. Since brain cells in cultures could be more easily influenced by nutrition than in vivo, effects of varying levels of essential fatty acids in the medium were also studied. Astroglial cells from cerebral hemispheres of newborn rats had a fatty acid composition of major phospholipids resembling that of whole brain. Addition of essential fatty acids to the medium profoundly altered the composition of cell membranes, contrary to what is found in whole animal experiments. Ethanol, in graded levels up to 75 mmol/l and added daily up to 8 days, did not significantly change the fatty acid composition of phosphatidylcholine and phosphatidylethanolamine. The ratio between neutral and acidic phospholipids diminished, which was more pronounced after 8 days of ethanol exposure than after 3 days. This study on ethanol exposure on glial cells focuses on the importance of nutritional composition of culture media and on the role of dynamics among phospholipid classes.

Homeoviscous adaptation under pressure. III. The fatty acid composition of liver mitochondrial phospholipids of deep-sea fish

Homeoviscous adaptation of biological membranes to high hydrostatic pressure has been investigated by determining the differences in lipid composition of membranes from fish obtained from depths between 200 and 4000 m. The fatty acid composition of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine/inositol and cardiolipin from a liver mitochondrial fraction was analysed by capillary gas-liquid chromatography. The ratio of saturated to unsaturated fatty acids significantly and negatively related to depth in PC and PE as predicted by homeoviscous adaptation to pressure. Thus, deep sea species possess greater proportions of unsaturated fatty acids than shallow species. Cardiolipin showed the opposite trend. An unsaturation index was not significantly related to depth in any phospholipid fraction.