Lipids of subcellular particles

Methods for isolation and characterization of subcellular particles as well as procedures for analysis of lipid class composition are discussed. The literature on distribution of lipids in subcellular particles is then reviewed. Pertinent new data from our laboratories are presented as well. The isolated particles are related to the organelles to which they correspond in the cell and are discussed with regard to heterogeneity and morphological integrity. Confusion can arise with regard to subcellular particles unless it is appreciated that: 1) preparation of particles of high purity generally requires more than the classical differential centrifugation scheme (both differential and gradient centrifugation may be required); 2) it is hazardous to apply exactly the same procedure for all tissues; 3) all subcellular fractions must be thoroughly characterized. The more recently devised DEAE cellulose column and thin-layer chromatographic procedures for analysis of lipid class composition are more reliable than the older hydrolytic or silicie acid column or paper chromatographic techniques. The chief lipid components of mitochondria from all organs and species are lecithin, phosphatidyl ethanolamine, and cardiolipin (diphosphatidyl glycerol). Despite the fact that reports in the literature are in agreement that phosphatidyl inositol is a major component of mitochondria, it is concluded on the basis of new data obtained from highly purified mitochondria and improved analytical methods that phosphatidyl inositol is not a major component of mitochondria. The presence of a relatively large amount of phosphatidyl inositol in mitochondrial preparations is probably related in part to contamination with other particles. Some analytical procedures are demonstrated to give erroneous values for this lipid class. It is also concluded that phosphatidyl serine, phosphatidic acid, sphingomyelin, cerebrosides, and lysophosphatides, reported to occur in mitochondria, are not characteristic mitochondrial components and furthermore that the large amount of uncharacterized mitochondrial phospholipid reported is actually an analytical artifact. Microsomes appear to be similar to mitochondria except that cardiolipin is either low in or absent from microsomes. Available data indicate nuclei to be rather similar to mitochondria and microsomes, at least in some organs. Studies of the fatty acids of subcellular particles indicate that different particles from one organ have very similar fatty acid compositions. It is clear that there are marked variations in fatty acid composition of particles from different organs and from different species. Differences in dietary fat may be associated with marked changes in fatty acid composition, although brain mitochondrial lipids are largely unchanged. Each lipid class from mitochondria of most organs appears to have a fairly characteristic fatty acid composition. Cardiolipin from some organs contains primarily linoleic acid, phosphatidyl ethanolamine contains large amounts of linoleic and higher polyunsaturates, and lecithin is similar to phosphatidyl ethanolamine except that it does not contain as much arachidonic acid and/or other highly unsaturated fatty acids. New data, the first to be reported, are presented for heart mitochondrial cardiolipin, phosphatidyl ethanolamine, and lecithin. It is concluded that there are two basically different types of membranous structures. Myelin is the chief representative of the metabolically stable type of membrane structure while mitochondria represent the more labile type. The two types of membranes have very different in vivo properties and very different lipid compositions. Myelin is characterized by a high content of cholesterol and sphingolipids with more long chain saturated or monoenoic fatty acids while mitochondria are characterized by a low cholesterol content, little or no sphingolipid, and highly unsaturated fatty acids. It is clear that formulations of the myelin type membrane structure such as that of Vandenheuvel cannot apply to mitochondria. It is postulated that membrane structures intermediate between the extremes represented by myelin and mitochondria exist.     

The effect of diet on the phospholipid composition of the red blood cells of man

Short term (16 day) controlled fat (formula type diet) feeding to 10 healthy adult males led to no detectable change in the total amt or the relative proportions of the individual phospholipids of the red blood cells, although limited changes did occur in the fatty acids of certain of the phospholipids. The total phospholipid content of the red blood cells was 315±10 mg/100 ml (average of 20 samples). Lecithin accounted for 34% of the total, with sphingomyelin, phosphatidyl ethanolamine and phosphatidyl serine representing 25, 25 and 16%, respectively. Approx 36% of the phosphatidyl ethanolamine, 4% of the phosphatidyl serine and 6% of the lecithin was present in the plasmalogen form. Each phospholipid class was found to have a distinctive fatty acid spectrum. The M ratio of saturated to unsaturated fatty acids in all three phosphoglycerides was nearly 1:1. Behenic, lignoceric and nervonic acids made up almost half of the sphingomyelin fatty acids, and the M ratio of saturated to unsaturated fatty acids in this lipid was 3:1. When compared with red cells from subjects consuming a diet with a high butter fat content, red cells from subjects on a diet rich in corn oil were found to contain higher levels of linoleic acid in the lecithin and phosphatidyl serine fractions, and lower levels of oleic acid in the lecithin fraction. No changes were observed in the fatty acids of the phosphatidyl ethanolamine and sphingomyelin fractions. It is probable that these alterations represent the result of highly specific exchanges with plasma fatty acids, and it is suggested that three levels of specificity are involved: class of phospholipid, type of fatty acid, and specific fatty acid.     

Studies on lipid and fatty acid composition of human hepatoma tissue

Studies are reported on the composition of the lipids of human liver and hepatoma tissues from male adults. Liver tissues were obtained from individuals who died from causes other than liver disease or cancer. The hepatoma tissues were obtained from individuals shortly after they succumbed to cancer. The total lipid of each tissue was fractionated quantitatively by silicic acid column chromatography into neutral lipid, glycolipid, and phospholipid fractions. These fractions were analyzed by thin layer chromatography and converted to methyl esters for analysis of their constituent fatty acids by gas liquid chromatography. In comparison to liver tissue, the total amount of lipid in the hepatoma tissues was generally higher and more variable; the lipid of one hepatoma was ca. 92% of the dry wt of the tissue. The greater lipid content of the hepatoma tissues was due to the high percentage of neutral lipid. Except for one specimen, there was ca. the same amount of glycolipid in the hepatoma as in the liver tissues, but the composition of the glycolipid fraction of the hepatoma lipid differed considerably, particularly in the ganglioside fraction. The phospholipid fraction of hepatoma lipid was much lower than that of liver but exhibited only quantitative differences in composition. No glyceryl ether diesters and only traces of plasmalogens of phosphatidyl choline or phosphatidyl ethanolamine were detected in the liver and hepatoma lipids. The levels of monoenoic acids were higher and those of linoleic and polyunsaturated fatty acids lower in the hepatoma lipids. Positional isomers of trienoic acids not normally present in liver tissue were detected in hepatoma lipids. The abnormalities observed in lipid composition indicated interferences in the regulatory processes of lipid metabolism in human hepatoma similar to those observed in animals.     

Distribution of cholesteryl esters and other lipid in subcellular fractions of the adrenal gland of the pig

Total lipids from whole pig adrenal glands as well as from their mitochondria, microsomes, liposomes, and cell sap were extracted and fractionated first into neutral lipids and phospholipids. The highest percentage of neutral lipids was found in the cell sap, and the lowest in the microsomal fraction. Neutral lipids were subfractionated into cholesteryl esters, free cholesterol, triglycerides, and free fatty acids. Cholesteryl esters were distributed throughout the liposomes. Free fatty acids represented a substantial part of cell sap lipids, but were present also in the mitochondria, microsomes, and liposomes. Fatty acids of all fractions were analyzed by gas liquid chromatography. Free fatty acids and cholesteryl ester fatty acids from all cellular fractions were similar in composition and were characterized by considerable quantities of linoleic and arachidonic acid. Triglycerides were characterized by an increased percentage of palmitic and a low content of arachidonic acid. Phosphatidyl choline, phosphatidyl ethanolamine, diphosphatidyl glycerol, and sphingomyelin plus phosphatidyl inositol were isolated from the lipids by preparative thin layer chromatography, and their fatty acids analyzed by gas liquid chromatography. Phosphatidyl choline and phosphatidyl ethanolamine from mitochondria, microsomes, and cell sap were very similar in respect of their fatty acid composition. Sphingomyelin plus phosphatidyl inositol was characterized by a high content of C22:2omega6. Diphosphatidyl glycerol was present in mitochondria and in the cell sap.     

Lipid composition of beef and human pituitary glands

The lipid composition of beef and human pituitary was determined by chromatographic and spectrophotometric methods. Beef pituitary lipid contained about 25% nonpolar lipids and 75% phospholipids whereas nonpolar lipids made up approximately 60% of the total in human pituitaries. The main nonpolar (i.e., low polarity) lipids in human pituitary were triglycerides, cholesterol, free fatty acids and an unidentified component in the triglyceride fraction. Cholesterol was the major nonpolar lipid component in freshly collected beef anterior and posterior pituitary, but the amount of free fatty acids appeared to increase during storage. Preliminary investigation of the unknown nonpolar lipid in human pituitaries suggested that it was an unsaturated hydroxy compound with no carbonyl functions. Thin layer chromatography indicated that it was also present in smaller amounts in freshly collected beef pituitaries. The main phospholipids of beef anterior, posterior and human pituitary were phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl inositol, phosphatidyl serine and sphingomyelin. The fatty acid composition of total nonpolar lipids, free fatty acids, total phospholipids, phosphatidyl ethanolamine and phosphatidyl choline of beef anterior and posterior pituitary was determined by gas liquid chromatography. Mixtures of saturated and unsaturated fatty acids ranging from C₁₂ to C₂₂ were present; the main fatty acids were palmitic, stearic, oleic, linoleic and arachidonic.     

Lipid composition of 30 species of yeast

The detailed composition of cellular lipid of more than 23 species of yeast has been determined quantitatively by thinchrography on quartz rods, a method previously used for estimating cellular lipids of seven species of yeast. That data was fortified by neutral and phospholipid quantitations on 30 species of yeast cells. Most of the test organisms contained 7–15% total lipid and 3–6% total phospholipid per dry cell weight, except for the extremely high accumulation of triglycerides in two species ofLipomyces. Qualitatively, 30 species of yeast cells contained similar neutral lipid constituents (triglyceride, sterol ester, free fatty acid, and free sterol) and polar lipid components (phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl inositol, cardiolipin, and ceramide monohexoside) without minor constituents. Based on the quantitative composition of neutral lipids, the 30 species of yeast were divided into two groups, the triglyceride predominant group and the sterol derivative group. These groupings were fairly well overlapped from the standpoint of the distribution characteristics of fatty acid. The relative polar lipid compositions also grossly resembled each other. Only one exception of polar lipid composition in yeast cells was found inRhodotorula rubra species which contained phosphatidyl ethanolamine as the most abundant phospholipid. Fatty acid distribution patterns in yeast cells consistently coincided with other reports concerning fatty acid composition of yeast cells. Correlation of lipid composition and classification of yeasts are suggested and discussed. A part of this investigation has been reported at the 14th conference of the Japan Oil Chemists' Society, Nagoya, Japan, October 1975.     

The lipid composition of microsomal preparations from lactating bovine mammary tissue

The microsomes isolated from lactating bovine mammary tissue contained 4.3 mg lipid per milligram nitrogen. Phospholipids comprised 83% of the lipids. The neutral lipids were composed of triglycerides (20–30%), diglycerides (5–10%), free fatty acids (15–30%, cholesterol (35–40% and cholesterol esters (10–12%, respectively. Phosphatidylcholine was the predominant phospholipid component (>50%), and the remainder consisted of phosphatidylethanolamine (21–13%), phosphatidylserine (4–6%), phosphatidylinositol (8%), sphingomyelin (9%) and lysophosphatidylcholine (2%) respectively. The composition of the microsomal phospholipids was similar to that of isolated mammary cells and tissue homogenates but quite different from milk and fat globule membrane phospholipids. The triglycerides contained short chain fatty acids but their relative concentrations were lower than in milk triglycerides. The various lipid fractions had a variable proportion of saturated fatty acids, i.e., triglycerides (47.7%), diglycerides (86.7%), free fatty acids (70.6%), phosphatidylcholine (50.6%), phosphatidylethanolamine (50.8%), phosphatidylserine (35.3%), phosphatidylinositol (40.5%) and sphingomyelin (82.3%), respectively. The molecular distribution of fatty acids in the microsomal triglycerides and phosphatidylcholine was similar to that occurring in milk, i.e., the short chain and unsaturated fatty acids were concentrated in the primary positions (sn1 andsn3) of the triglycerides, and the unsaturated acids were preferentially located in positionsn2 of the phosphatidylcholine. The compositional data indicate that mammary microsomes are not the direct source of the phospholipids of the milk fat globule.     

Studies on liver phosphatidyl cholines: II. Effect of sex,age and species differences on phosphatidyl cholines from liver mitochondria and microsomes

Liver mitochondrial and microsomal phosphatidyl cholines differing in the degree of unsaturation of their fatty acids have been separated into four fractions by silver ion silica gel TLC. The levels of the four phosphatidyl choline fractions were determined for male and female rats and mice, fetal and young rabbits, and female hamsters and guinea pigs. The sum of phosphatidyl choline fractions 1, 2, and 3 of mitochondria and microsomes was greater in the female rat than in the male rat with the difference being a reflection of a higher level of fraction 3 which contains arachidonic acid. The female rat has greater concentration of phosphatidyl choline fractions 1 and 3 of mitochondria. Similar results were seen in mouse liver microsomes but not in mitochondria. The levels of the individual four fractions varied from species to species. No change occurred in the levels of the phosphatidyl choline fractions of fetal (−9 and −3 days) rabbits, but an increase was seen in the level of fraction 4 between day 3 and day 35 in both the mitochondria and microsomal fractions of liver. The concentration of mitochondrial and microsomal protein, total phospholipid and total lecithin phosphorus were determined in rat, mouse, hamster and guinea pig. The total phospholipid phosphorus/protein (μg/mg) of microsomes was greater in all species than that observed in mitochondria. Liver microsomes contain 45–50% of total phospholipid phosphorus as lecithin whereas mitochondria contains 32–37%. The fatty acid patterns of mitochondria and microsomal phosphatidyl cholines were determined and the ratio of palmitate to stearate was greater than two for mice and hamsters and approximately 0.5 for rat and guinea pigs.     

Lipids of some thermophilic fungi

Total lipid content in the thermophilic fungi—Thermoascus aurantiacus, Humicola lanuginosa, Malbranchea pulchella var.sulfurea, andAbsidia ramosa—varied from 5.3 to 19.1% of mycelial dry weight. The neutral and polar lipid fractions accounted for 56.4 to 80.2% and 19.8 to 43.6%, respectively. All the fungi contained monoglycerides, diglycerides, triglycerides, free fatty acids, and sterols in variable amounts. Sterol ester was detected only inA. ramosa. Phosphatide composition was: phosphatidyl choline (15.9–47%), phosphatidyl ethanolamine (23.4–67%), phosphatidyl serine (9.3–17.6%), and phosphatidyl inositol (1.9–11.9%). Diphosphatidyl glycerol occurred in considerable quantity only inH. lanuginosa andM. pulchella var.sulfurea. Phosphatidic acid, detected as a minor component only inM. pulchella var.sulfurea andA. ramosa, does not appear to be a characteristic phosphatide of thermophilic fungi as suggested earlier. The 16∶0, 16∶1, 18∶0, 18∶1, and 18∶2 acids were the main fatty acid components. In addition,A. ramosa contained 18∶3 acid. Total lipids contained an average of 0.93 double bonds per mole of fatty acids, and neutral lipids tend to be more unsaturated than phospholipids.     

Composition of the neutral and phospholipid fractions from ginkgo nuts (Ginkgo biloba) and fatty acid composition of individual lipid classes

The purified lipid fraction (1.26% on the wet weight basis) from the nuts ofGinkgo biloba was found to be 90.6% neutral lipids, 7.5% polar lipids, and a very small amount of glycolipids. Main fatty acids in the triglyceride fraction were oleic and linoleic acids, and those in the phospholipid fraction were palmitic acid in addition to these unsaturated acids. The enzymic hydrolysis of the triglyceride and individual phospholipid fractions showed that only the triglyceride and phosphatidylcholine fractions contained relatively large amounts of unsaturated acids in their β-positions. The gas liquid chromatography-mass spectrometric analysis of the fatty acids of the steroid ester fraction indicated the presence of lignoceric, cerotic, montanic, and melissic acids as well as a lactone and compounds suspected to be phenolic acids containing long chain diols.     

Polar lipids ofMacrophomina phaseolina

Macrophomina phaseolina was grown on a defined medium at three different carbon/nitrogen ratios. The lipids of the mycelia and the sclerotia were extracted; fractionated into polarity groups; and separated by thin layer, column, and gas liquid chromatographies. Sclerotia contained higher levels of neutral lipids and lower amounts of polar lipids than mycelia. The neutral lipid content of sclerotia increased, up to 77% of total lipids, and phospholipids decreased as carbon/nitrogen ratio increased from 10 to 320. The glycolipid content was not altered significantly by changes in carbon/nitrogen ratios. Although cardiolipin could not be detected in sclerotial polar lipids, both sclerotia and mycelia contained similar phospholipid profiles with major quantitative differences. Phosphatidic acid and phosphatidyl glycerol were major components of sclerotia, whereas phosphatidyl ethanolamine and phosphatidyl inositol were the major phosphatides of mycelia. Phosphatidyl choline was present in both mycelia and sclerotia. The fatty acid distribution did not show any particular pattern of saturation or unsaturation due to differences in carbon/nitrogen ratio. However, mycelial lipids tended to contain C24∶1, C18∶3, and C22∶1 as major fatty acids, whereas the major fatty acids in sclerotial lipids were C18∶2, C18∶1, C22∶1, C20∶0, and C16∶1. Saturated fatty acids were present in lesser concentrations.     

Analysis of subcellular phosphatidyl choline in developing rabbit lung

Phosphatidyl choline is a major lung surfactant. Insufficient development of the surfactant in neonates is often associated with the Respiratory Distress Syndrome. The concentration and fatty acid composition of phosphatidyl choline have not been studied in the subcellular organelles of the developing lung. This study has investigated the development of the concentration and fatty acid composition of phosphatidyl choline in subcellular fractions of 28-day and 30-day fetal and maternal New Zealand rabbit lungs. The concentration of total phospholipids in lamellar bodies increased four to five fold from 28-day fetus to 30-day fetus which, in turn, was similar to the maternal level. Total phospholipid content increased only about 50% in mitochondria and microsomes. The percentage of phosphatidyl choline among total phospholipids in lamellar bodies increased successively from 60% at 28 days gestation to 84% at 30 days gestation and leveled at 84% in maternal lamellar bodies. Microsomal PC increased steadily from 52% in the 28-day fetus to 65% in the adult. Analysis of the fatty acid composition of phosphatidyl choline in lamellar bodies confirmed 16∶0 as the major fatty acid, and its content remained constant from 28 days gestation to adult. In contrast, the content of 16∶0 of the microsomal phosphatidyl choline decreased with increasing gestation. Changes of several unsaturated fatty acid components were observed in both lamellar bodies and microsomes in the developing lungs. Maturational development of phosphatidyl choline is reflected in an increase in the concentration of this surfactant, particularly in lamellar bodies, and possibly in remodeling of fatty acid composition in both lamellar bodies and microsomes.     

Biochemical Studies on Whey Lipid Substances

The present work was undertaken to determine the lipid materials of salted and unsalted whey as a byproduct of cheese industry. The general chemical analysis show that the salted whey contained lower amounts of lactase, proteins and lipids compared with unsalted whey. Whey lipids contained palmitic and oleic acids as the most abundant saturated and unsaturated acids, respectively. The presence of salt quantitatively altered the concentration of short-chain fatty acids due to its salting out phenomenon. A wide variety of hydrocarbons was found and C₂₂, C₂₃ constituted over 75% of the total hydrocarbons. The presence of salt in whey remarkably changed the hydrocarbon profile. The most predominant phospholipid was phosphatidyl choline followed by phosphatidyl inositol. Once more, the salt changed qualitatively and quantitatively the whey phospholipid pattern and led to precipitate some of the highly polar phospholipids with cheese during milk processing.     

Effect of low methionine,choline deficient diets upon major unsaturated phosphatidyl choline fractions of rat liver and plasma

To see how the metabolism of specific phosphatidyl choline fractions might be affected when only a limited source of methyl groups was available, rats were fed for 7 days a low methionine, cholinedeficient diet or one supplemented with either choline or methionine. Prior to killing, they were injected with¹⁴C-methyl methionine and liver and plasma phosphatidyl choline isolated and separated by argentation chromatography into 3 major unsaturated fractions. Fatty acid composition and radioactivity of the fractions were determined. Deficient rats had reduced total liver phosphatidyl choline when compared with the supplemented groups, but the proportions of 20∶4 and 22∶6 fatty acids in the total phosphatidyl choline were unchanged. Plasma phosphatidyl choline also was reduced sharply by the deficiency, as was its proportion of 20∶4 fatty acid. Specific activities of the liver 22∶6, 20∶4, and 18∶2 phosphatidyl choline fractions showed that deficient rats had less radioactivity in their 20∶4 and 18∶2 phosphatidyl choline than did the supplemented animals. Plasma phosphatidyl choline fractions presented a similar pattern. Feeding methionine or choline nearly doubled radioactive methyl group incorporation into the 20∶4 phosphatidyl choline fraction of liver and plasma, while incorporation into the 22∶6 phosphatidyl choline was reduced or unchanged. The results suggested that, in the rat, limited availability of methyl groups altered the metabolism of liver and plasma phosphatidyl choline fractions. Methionine, as a source of labile methyl groups, appears necessary for the normal synthesis of certain unsaturated phosphatidyl choline fractions (particularly 20∶4 phosphatidyl choline). Transmethylation of phosphatidyl ethanolamine molecular species to the corresponding phosphatidyl choline species may be an important reaction in normal lipid metabolism and transport. Relative affinities for incorporation of the labeled methyl groups into the phosphatidyl choline fractions of either deficient or supplemented rats were: 22∶6>20∶4>18∶2.     

Lipid metabolism ofAgaricus bisporus (Lange) sing.: I. Analysis of sporophore and mycelial lipids

The lipid components of four strains ofAgricus bisporus (Lange) Sing., the cultivated mushroom, were analyzed. Both sporophore and mycelial samples were obtained from beds in normal production. A method for obtaining mycelium free of compost was developed. Neutral lipids were separated from polar lipids by silicic acid column chromatography. Each fraction was separated by thin layer chromatography. Fatty acid methyl esters were analyzed by gas liquid chromatography and mass spectrometry. Sporophore extracts contained free sterol, free fatty acid, triglycerides, phosphatidyl choline and phosphatidyl ethanolamine. High amounts of linoleic acid were found in both neutral and polar lipid fractions. Mycelial extracts contained free fatty acids, triglycerides, phosphatidylcholine and phosphatidyl ethanolamine. No free sterol could be detected. Linoleic acid was also present in large amounts. Paper 3798 in the Journal Series of The Pennsylvania Agricultural Experiment Station.     

Reaction of anti-phosphatidyl inositol antisera with neural membranes

Ca. 15% of the phosphatidyl inositol in myelin and microsomal membranes from rat brain was detectable by antiphosphatidyl inositol antibody. Antibody-detectable phosphatidyl inositol in myelin and microsomes readily increased when the membranes were incubated at 45 C with the antiserum. Synaptic membranes also had only a limited capacity to adsorb antibody. Quantitative binding studies with synaptic membranes and mitochondria were limited, because these membranes contain cardiolipin, which cross reacts with phosphatidyl inositol antisera. Moreover, highly purified synaptic and mitochondrial membranes contain appreciable amounts of other membrane fractions.     

Influence of microwave roasting on positional distribution of fatty acids of triacylglycerols and phospholipids in sunflower seeds (Helianthus annuus L.)

Whole sunflower seeds were exposed to microwave roasting for 6, 12, 20 or 30 min at a frequency of 2450 MHz. The kernels were then separated from the sunflower seeds, and the lipid components and the positional distribution of fatty acids in triacylglycerols (TAGs) and phospholipids (PLs) were investigated. Major lipid components were TAGs and PLs, while steryl esters, free fatty acids and diacylglycerols were also present in minor proportions. The greatest PL losses (p < 0.05) were observed in phosphatidyl ethanolamine, followed by phosphatidyl choline or phosphatidyl inositol. Significant differences (p < 0.05) in fatty acid distributions occurred (with few exceptions) when sunflower seeds were microwaved for 20 min or more. Nevertheless, the principal characteristics for the positional distribution of fatty acids still remained after 20 min of microwave roasting; unsaturated fatty acids, especially linoleic, were predominantly concentrated in the sn‐2‐position and saturated fatty acids, especially stearic and palmitic acids, primarily occupied the sn‐1‐ or sn‐3‐position. These results indicate that no significant changes in fatty acid distribution of TAGs and PLs would occur within 12 min of microwave roasting, ensuring that a good‐quality product would be attained.     

Fatty acid composition of serum lipids in fasting ponies

Alterations in the fatty acid distribution of total lipid extracts and 4 of the major lipid subclasses of serum in ponies fasted overnight and for 4 and 7 days were determined. Although increases in 16:0, 16:1, and 18:3 omega 3 were observed, decreased amounts of 18:0 and 18:2 omega 6 combined to cause no significant change in the saturated to unsaturated fatty acid ratio in the total extracts. Phospholipid became somewhat preferentially enriched in saturated fatty acids due to a decrease in 18:1, although this response was variable. The free fatty acid and triglyceride fractions both showed increases in relative amounts of 18:3 omega 3 and a decrease in 18:0 and a concomitant change in the saturated to unsaturated fatty acid ratio. This endogenous alteration was most likely due to the mobilization of an increased proportion of polyunsaturated fatty acids from tissue sites with their subsequent incorporation into triglyceride by the liver. It probably reflects the type of forage diet on which the animals had been maintained prior to the study. The fatty acid composition of the cholesteryl ester fractions was unchanged during fasting but contained appreciable amounts of the 18:2 omega 6 fatty acid.     

Studies on liver phosphatidyl cholines: I. Effects of fatty liver induction on phosphatidyl cholines from liver mitochondria and microsomes

Protein, total phospholipid, phosphatidyl cholines and phosphatidyl choline fractions from liver mitochondria and microsomes of female rats were analyzed after treatment with CCl₄ (0.3 ml of CCl₄ suspended in corn oil) or ethionine (50 mg in 0.9% saline) or after feeding a choline deficient, low protein diet for seven days. Phosphatidyl cholines were separated into four fractions differing in the degree of fatty acid unsaturation. Over 50% of total phosphatidyl choline phosphorus was present in fraction 3 of liver mitochondria and microsomes. The major fatty acid in fraction 1 was docosahexaenoic acid. Fraction 4 contains oleic and linoleic acids. Arachidonic acid occurs in fraction 2 and 3. Ethionine decreased the amount of microsomal protein and phosphatidyl choline fraction 1 of mitochondria. Microsomal protein was decreased by CCl₄. The choline deficient, low protein diet caused a decrease in mitochondrial and microsomal phospholipids. The amount of the mitochondrial phosphatidyl choline decreased. Corn oil increased the level of phosphatidyl choline fraction 3. Choline deficiency decreased the amount of phosphatidyl choline fraction 3, increased fraction 4 of mitochondria and microsomes and increased fraction 1 of microsomes.     

Fatty acid composition of rat hearts as influenced by age and dietary fatty acids

Fatty acid composition of neutral and polar lipid fractions from rat hearts was determined in rats of different ages as their diet source changed. Piebald rats were weaned at 21 days and were fed standard lab chow. Lipids from rat hearts, mothers milk and lab chow were purified on a Sephadex G-25 fine column and separated into neutral and polar lipid fractions by silicic acid column chromatography. These lipid fractions were then hydrolyzed and methylated with BF₃ in methanol, prior to gas liquid chromatographic separation on a 1/8 in. × 10 ft aluminum column of 15% EGS on 80–100 mesh acid-washed Chromosorb W. Three major fatty acids in the neutral lipid fraction comprised 72% of total neutral lipid fatty acids from young hearts. At sexual maturity (at least 74 days old) C_18∶1 was the major fatty acid, followed by C_16∶0 and C_18∶0. The same three fatty acids comprised 83% of total polar lipid fatty acids, but C_18∶0 was the major fatty acid, followed by C_16∶0 and C_18∶1. The fatty acid composition of dietary lipids influenced the total neutral lipid fatty acid composition of the rat heart, but had little influence on the fatty acid composition of the polar lipid fraction. Presented in part at the AOCS Meeting, New Orleans, April 1970.