Fatty acids in phospholipids isolated from human red cells

Total lipids of packed erythrocytes from healthy men 22 to 25 years old were extracted with chloroform-methanol mixture. Phospholipid classes were separated from neutral lipids and pigments on a silicic acid column. Phosphatidyl inositol (PI) was freed of its contaminants phosphatidyl ethanolamine (PE) and phosphatidyl serine (PS) on an aluminum oxide column. Additional silicic acid columns with modified solvent systems were needed for complete separation of other overlapped phospholipid classes. The identification of phospholipids in each eluted fraction was accomplished by TLC, using the appropriate spray tests and reference compounds, and confirmed on each of the isolated phospholipids by IR spectrophotometry. The total content of phospholipids as determined by phosphorus analysis was found to be 2.63 mg/ml of packed cells. These phospholipids were found to have the following composition (in per cent of total phospholipid): PI, 2.3; PE, 13.4; ethanolamine plasmalogen (EP), 14.5; PS, 3.9; lecithin (L), 34.2; choline plasmalogen (CP), 1.4; sphingomyelin (Sph), 28.4 and lysolecithin (LL), 1.7. The fatty acid composition of each phospholipid was determined by GLC. The average number of double bonds per fatty acid in the isolated phospholipids was found to be as follows: PI, 1.5; PE, 1.9; EP, 3.6; PS, 2.1; L, 1.0; CP, 2.0; Sph, 0.2 and LL, 0.5. The positional distribution of fatty acids in both L and PE was ascertained by selective enzymatic hydrolysis with phospholipase A. Saturated fatty acids of L were esterified predominantly in the α′-position, whereas in PE only 63.9 mole per cent of the saturated fatty acids were found in this position. Presented in part at the AOCS Meeting in Los Angeles, April 1966. Dept. of Health, Education and Welfare, USPHS.     

Positional Distribution of Fatty Acids on Oilseed Phosphatidylcholines and Phosphatidylethanolamines

Positional distribution of fatty acids in the phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs) of coriander (Coriandrum sativum), carrot (Daucus carota), papaya (Carica papaya), palash (Butea monosperma), sunflower (Helianthus annuus), karanja (Pongamia glabra) and jangli badam (Sterculia foetida) seeds was studied. PCs and PEs contained 58 to 83% of unsaturated fatty acids. The fatty acids liberated by phospholipase A₂ hydrolysis from 2-position consisted mainly of unsaturated acids. The PC and PE classes namely US, SU and UU in terms of saturated (S) and unsaturated (U) fatty acids in the 1- and 2-positions were calculated from the proportions of saturated fatty acids in total PC/PE and in the 2-position. The amount of disaturated class was absent in all PCs and PEs as determined by mercuric acetate adduct formation and subsequent TLC separation. SU and UU classes were found to be predominant in all PCs and PEs.     

Properties of diacylglycerol kinase purified from bovine brain

A nearly homogeneous but somewhat unstable diacylglycerol kinase (ca. MW 72,000 daltons) was purified from bovine brain by modification of the procedure of Kanoh et al. (Kanoh, H., Kondoh, H., and Ono, T. [1983]J. Biol. Chem. 258, 1767–1774). The purification consisted of four steps (brain cytosol isolation and successive chromatography on DEAE-cellulose, Sephadex G-25 for desalting and ATP-agarose) carried out in buffers stabilized with EDTA, ATP and dithiothreitol (DTT). Specific activities, determined within 4 hr of purification, ranged from 908–1857 nmol ATP incorporated/min/mg protein, with the variation reflecting the instability. Optimal activities required deoxycholate (0.1%), one of the phosphoglycerides [phosphatidylcholine (PC), phosphatidylethanolamine (PE) or phosphatidylserine (PS)] (0.025–0.25 mM), ATP (5 mM, apparent K_m=0.57 mM), 1,2-dioleoyl-rac-glycerol (5 mM, apparent K_m=1 mM) and Mg²⁺ (10 mM, apparent K_m=2.2 mM). Phosphatidylinositol (PI) was slightly less effective than PC, PE or PS and noninhibitory in combination with PC, PE or PS. Relative to PC phosphatidic acid (PA) (52%), sphingomyelin (48%), lyso-PC (1.5%) and lyso-PI (28.6%) were less effective activators. The sulfhydryl reagents,p-chloromercuribenzoic acid (PCMB) (1.0 mM),N-ethylmaleimide (NEM) (1.0 and 2.0 mM) and 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) (1.0 mM), showed strong inhibition of activity which was prevented by 0.5 mM DTT. In contrast to other reports, this purified enzyme showed no monoacylglycerol kinase activity. Comparison of diacylglycerols of varying fatty acid composition indicated that the enzyme showed a preference for substrates with at least one unsaturated fatty acid, particularly in the 2-position. With saturated fatty acids the order of preference was C₁₀ and C₁₂>C₁₄>C₁₆>C₁₈. Such a pattern indicates that the enzyme shows little selectivity that favors the generation of particular molecular species of PA.     

Composition and structure of phospholipids in chicken muscle tissues

Lipids extracted from breast muscle and thigh muscle of one-year old chickens on a standard MSU-Z-4 diet have been fractionated by silicic acid column chromatography into nonphospholipids, phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl choline (lecithin), and sphingomyelins. Phospholipid fractions were identified by thin-layer chromatography and the quantity of each determined by gravimetric analysis, analysis of the phosphorus content, and infrared spectra. The phospholipid content of thigh muscle (dark meat) lipids was higher than that in the breast muscle (white meat). Phosphatidyl choline and phosphatidyl ethanolamine were found in relatively greater amts than phosphatidyl serine and sphingomyelins. Enzymatic hydrolysis followed by gas-liquid chromatographic analysis of the fatty acids liberated and those in the lysocompounds was used to establish the positional specificity of the fatty acids in the phosphoglycerides. The polyunsaturated fatty acids are located primarily at the β-position and the saturated fatty acids at the α′-position. The qualitative and quantiative determination of the plasmalogens was also accomplished. Michigan Agriculture Experiment Station Journal Article No. 3527. Presented at the AOCS Meeting in Chicago, October, 1964.     

Molecular species composition of the major diacyl glycerophospholipids from muscle,liver, retina and brain of cod (Gadus morhua)

The molecular species composition of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) from white muscle, liver, retina and brain of cod (Gadus morhua) were determined by high-performance liquid chromatography of the respective 1,2-diacylglycerol 3,5-dinitrobenzoyl derivatives. A minimum of 69 diacyl species was identified. In muscle and liver saturated fatty acid/polyunsaturated fatty acid (PUFA) and monounsaturated fatty acid/PUFA molecular species were predominant, particularly 16∶0/20∶5 and 16∶0/22∶6 in PC, 16∶0/22∶6 and 18∶1/22∶6 in PE and 18∶0/22∶6 and 18∶1/22∶6 in PS. Didocosahexaenoyl species were major components of PC, PE and PS from retina, comprising 29.3, 71.8 and 59.7% of the respective totals. Didocosahexaenoyl species were also abundant in PE and PS from brain, accounting for 13.8 and 24.0% of the totals, respectively. DiPUFA species were important in muscle, totalling 21.2% in PC and 38.3% in PE. PC from all tissues had the largest amounts of species containing only saturated or monounsaturated fatty acids, accounting for 59.8% of PC from brain, including 12.8% of 18∶1/24∶1 plus 24∶1/18∶1.     

On the specificity of a phospholipase A2 purified from the 106,000×g pellet of bovine brain

Assessment has been made of the specificity of a purified phospholipase A₂ from the 106,000×g pellet (microsomal fraction) of bovine grey matter which shows strong activity toward phosphatidylinositol (PI). In the first series of experiments involving the utilization as substrates of PI with different¹⁴C- or³H-labeled fatty acids in the 2-position, the purified phospholipase A₂ most readily removed 16∶0 palmitic acid, followed by 18∶0 stearic acid, 18∶1 oleic acid and 20∶4 arachidonic acid. In the second series of experiments, the purified phospholipase A₂ showed preferential action toward PI (100%) compared to phosphatidylcholine (PC, 62.5%), phosphatidic acid (PA, 32.6%), phosphatidylethanolamine (PE, 25.1%) and phosphatidylserine (PS, 21.5%), where each phosphoglyceride was labeled in the 2-position with [1-¹⁴C] oleic acid. In the third series of experiments, fatty acids were shown to cause inhibition of action of the purified phospholipase A₂ on 1-acyl, 2-[1-¹⁴C] oleoyl PI in the order 20∶4>18∶1>18∶0>16∶0 which is the reverse order to that just noted. In the final series of experiments, the addition of the phosphoglycerides PC, PE, PS and PA in amounts of 5 or 10 μM caused either no inhibition (PE, 2%), slight inhibition (PC, 15%) or reasonably significant inhibition (PA, 20% and PS, 40%) of action of the purified phospholipase A₂ on 1-acyl, 2-[1-¹⁴C]-oleoyl PI. The pattern of specificity observed for the purified phospholipase A₂ combined with its microsomal location are the expected properties of a phospholipase A₂ that might function in a deacylation-reacylation cycle for modifying the fatty acid distribution in PI.     

Phospholipid studies of marine organisms: New branched fatty acids fromStrongylophora durissima

The phospholipids of the spongeStrongylophora durissima were analyzed. The major phospholipids present were phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylglycerol (PG) and phosphatidylinositol (PI). The major fatty acid components of the phospholipids consisted of short chain (C₁₄−C₁₉) and very long chain (C₂₅−C₃₀) “Demospongic” acids. Three novel branched Δ⁵ monounsaturated acids,Z-19-methyl-5-pentacosenoic,Z-19-methyl-5-hexacosenoic andZ-19-methyl-5-heptacosenoic acids were encountered in the sponge. The 3-saturated counterparts of these compounds, 19-methylpentacosanoic, 19-methylhexacosanoic and 19-methylheptacosanoic acids, as well as 19-methylpentacosanoic and 20-methyloctacosanoic acids also are hitherto undescribed acids present in the sponge. Trace amounts of 2 very long chain acids also were detected and their structures tentatively assigned as 19,21-dimethylheptacosanoic and 20,22-dimethyloctacosanoic acids. The distribution of these fatty acids according to phospholipid head groups also was described.     

The α,β-distribution of oleic,linoleic and linolenic acids in cruciferae seed triglycerides

Correlation studies on lipolysis data from 24 species of Cruciferae seed triglycerides have revealed very regular positional distribution patterns for oleic, linoleic and linolenic acids. When the ratio % 18:1 in β-position/% 18:1 in total triglycerides for each species is plotted vs. the content of Category I acids (16:0, 18:0, plus all C₂₀, C₂₂ and C₂₄ acids) in the total triglycerides, a smooth curve is obtained. Application of suitable statistical procedures yields a best-fitting curve, from which an equation expressing the % 18:1 in the β-position as a function of the fatty acid composition of the total triglycerides can be derived. The % 18:1 in the α-position is then readily calculated by difference. Similar distinctive relationships have also been developed for linoleic and linolenic acids. Comparison of calculated and experimental results shows that the relationships developed here are considerably more accurate than the previous Gunstone-Mattson and Evans hypotheses for estimating the α,β-distributions of 18:1, 18:2 and 18:3 in Cruciferae seed triglycerides. Presented in part at the AOCS meeting in San Francisco, California, April 1969.     

Fatty acid composition of milk phospholipids. II. Sheep,Indian buffalo and human milks

Phospholipids were isolated from sheep, Indian buffalo, and human milks, and their fatty acid compositions determined by gas chromatography. The specific distributions of fatty acids in phosphatidyl cholines (PC) and phosphatidyl ethanolamines (PE) were determined after phospholipase A hydrolysis. Fatty acid compositions and specific distributions were similar in sheep and buffalo milk phospholipids, and compared closely with those of bovine milk. Human milk phospholipids, particularly PE, contained much larger amounts of polyunsaturated acids, but negligible amounts of branchedchain acids. Palmitic and oleic acids were evenly distributed in human milk PC and PE, whereas they were preferentially located in the α′ position in PC and PE of ruminant milks. The results are discussed in the context of current theories of lipid biosynthesis. Part I of this series is “Fatty Acids of Bovine Milk Glycolipids and Phospholipids, and Their Specific Distribution in the Diacylglycerophospholipids,” W. R. Morrison, E. L. Jack and L. M. Smith. JAOCS,42, 1142–1147 (1965).     

Composition and metabolism of fatty acids in phospholipids of density-separated red cells of rats

Fatty acid compositions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) and the rates of fatty acid esterification to these phospholipids (PL) were measured in intact rat red cell populations of different ages separated by density gradient centrifugation in order to clarify changes in membrane lipids of red blood cells during in vivo aging. Fatty acid compositions of PC and PE altered progressively as red cells became denser. Changes in unsaturated fatty acids occurred predominantly at the 2-position of PC and PE and those in saturated fatty acids at both positions. The esterification rates of 5 major fatty acids decreased as red cells became denser and those of oleic acid, linoleic acid and arachidonic acid to both PC and PE of fraction I cells (oldest cells) were 37–51% those of fraction IV cells (youngest cells). Reduction in the rates of fatty acid esterification appeared to occur in the course of red cell maturation because reticulocyte-enriched cell fractions showed 4.5–14.5 times higher rates of linoleic acid and arachidonic acid esterifications to PC and PE.     

Microwave roasting and positional distribution of fatty acids of phospholipids in soybeans (Glycine max L.)

Whole soybeans were exposed to microwave roasting for 6, 12, and 20 min at a frequency of 2,450 MHz and were studied not only for phospholipid composition but also for positional distribution of the fatty acids. During microwave roasting, the greatest rate of phospholipid losses (P<0.05) was observed in phosphatidylethanolamine (PE), followed by phosphatidylcholine (PC) and phosphatidylinositol (PI), respectively. Therefore, the effects of microwave roasting on the composition and positional distribution of the fatty acids are likely clearer in PE than in PC or PI. However, the principal characteristics for the positional distribution of fatty acids are still retained during microwave roasting: unsaturated fatty acids, especially linoleic, are predominantly concentrated in the 2-position, and saturated fatty acids, especially palmitic, primarily occupy the 1-position after 12 or 20 min of roasting. The results suggest that unsaturated fatty acids located in the 2-position are significantly protected from microwave roasting.     

On the composition of Iranian olive oil

Two samples of virgin olive oil and one sample of hexane-extracted husk oil coming from Iran were examined. The analyses included physical and chemical characteristics, the composition of total fatty acids and fatty acids at the glyceride 2-position by gas liquid chromatography (GLC) of methyl esters, the triglycerides composition calculation according to Vander Wal theory, the separation of the alcoholic fractions (sterols, 4-methylsterols, triterpene alcohols, triterpene dialcohols and aliphatic alcohols) of the unsaponifiable matter by thin layer chromatography (TLC), the quantitation and the composition of these fractions by GLC of TMS derivatives. The results were in line with data from literature for olive oils of different origin, with the exception of: a high content of unsaponifiable matter (1.75 and 1.95% for virgin oils, 5.33% for husk oil); a high amount of sterols for husk oil (562 mg/100 g oil); a low content of SE 30 apparent β-sitosterol for husk oil (91.1%); a low amount of triterpene dialcohols (1 mg/100 g oil) and triterpene alcohols (78 and 91 mg/100 g oil) for virgin oils; a content of cycloartenol (60.2–66.9%) higher than the 24-methylenecycloartanol one (22.8–26.6%; a content of C₂₄ linear saturated alcohol (33.9–38.0%) slightly higher than the C₂₆ alcohol one (29.3–32.8%).     

Relationship between dietary supply of long-chain fatty acids and membrane composition of long- and very long chain essential fatty acids in developing rat photoreceptors

The present study was designed to determine if dietary supply of long-chain fatty acid (LCFA, C20∶4n-6, and/or C22∶6n-3), reflecting levels that might be incorporated into infant formulas, influences the fatty acid composition of the visual cell membrane. The rod outer segment (ROS) of the retina was analyzed from rats fed diets varying in the ratio of 18∶2n-6 to 18∶3n-3 with or without 20∶4n-6 [arachidonic acid (AA)] and 22∶6n-3 (docosahexaenoic acid) from birth to six weeks of age. The level of very long chain fatty acids (VLCFA, C₂₄−C₃₆) was identified using gas chromatography and gas chromatography-mass spectrometry. In the ROS, the highest relative percent of AA was attained in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of animals fed 1% AA diet, whereas feeding 0.7% docosahexaenoic acid (DHA) diet significantly increased the DHA level in PC, phosphatidylserine, and phosphatidylinositol compared to feeding diets containing AA. VLCFA of n-6 and n-3 up to C₃₆ were found in PC, with the most abundant fatty acids being C₃₂ and C₃₄. In PC, phosphatidylserine and PE, the n-6 tetraenoic VLCFA level was highly increased in animals fed 1% AA compared to other dietary groups. This study suggests that dietary fat containing small amounts of AA or DHA is an important factor influencing membrane fatty acid composition of the visual cell during development. Based on a presentation at the AOCS Annual Meeting & Expo in San Antonio, Texas, May 7–11, 1995.     

Neutral lipids of chickpea flour and protein isolates

The neutral lipids composition of defatted chickpea flour and two types of protein isolates has been studied. The main compounds in neutral lipids are triacylglycerols, free fatty acids, and diacylglycerols. Other compounds present are wax esters, free fatty alcohols, and free sterols. The main fatty acids in neutral lipids are C_18:2 and C_18:1 among the unsaturated, and C_16:0 and C_18:0 among the saturated acids. Free and esterified alcohols range from C_16:0 to C_28:0, the majority being those with an even number of carbon atoms. Sterols observed are β-sito-sterol, campesterol, stigmasterol, and δ-5-avenasterol. Triacyl-glycerols are partially hydrolyzed, and the amounts of unsaturated sterols and unsaturated fatty acids are reduced as a result of the chemical treatment during production of the protein isolates.     

The effect of lyophilization on the solvent extraction of lipid classes,fatty acids and sterols from the oysterCrassostrea gigas

The lipid class compositions of adult Pacific oysters [Crassostrea gigas (Thunberg)] were examined using latroscan thin-layer chromatography/flame-ionization detection (TLC/FID), and fatty acid compositions determined by capillary gas chromatography and gas chromatography/mass spectrometry (GC/MS). The fatty acid methyl esters were separated using argentation TLC and also analyzed as their 4,4-dimethyloxazoline derivatives using GC/MS. Major esterified fatty acids inC. gigas were 16∶0, 20∶5n−3, and 22∶6n−3. C₂₀ and C₂₂ nonmethylene interrupted (NMI) fatty acids comprised 4.5 to 5.9% of the total fatty acids. The NMI trienoic fatty acid 22∶3(7,13,16) was also identified. Very little difference was found in the proportions of the various lipid classes, fatty acids or sterols between samples of adult oysters of two different sizes. However, significant differences in some of the lipid components were evident according to the method of sample preparation used prior to lipid extraction with solvents. Lyophilization (freeze drying) of samples led to a significant reduction in the amounts of triacylglycerols (TG) extracted by solvents in two separate experiments (7.0 and 52.5% extracted). Extracts from lyophilized samples had less 16∶0, C₁₈ unsaturated fatty acids, and 24-ethylcholest-5-en-3β-ol, while C₂₀ and C₂₂ unsaturated fatty acids comprised a higher proportion of the total fatty acids. There was no significant change in the amounts of polar lipids, total sterols, free fatty acids or hydrocarbons observed in extracts from lyophilized samples relative to extracts from nonlyophilized samples. Addition of water to the freezedried samples prior to lipid extraction greatly improved lipid yields and resulted in most of the TG being extracted.     

Evidence for diplasmalogen as the major component of rabbit sperm phosphatidylethanolamine

The question of whether diplasmalogens [1,2-di(O-1′-alkenyl) phosphatidyl derivatives] make up part of the plasmalogen component of cell phospholipids was examined using rabbit epididymal spermatozoa. These cells are readily obtained as a highly homogeneous suspension and long have been known to have high plasmalogen content. Phospholipids were determined by thin layer chromatography (TLC) with CuSO₄ staining. Plasmalogens were determined by hydrolysis of the phospholipids with TCA/HCl, followed by TLC and CuSO₄ staining. Ethanolamine derivatives were determined by ninhydrin. The phosphatidylethanolamine (PE) content of these cells was 29±2 μg/10⁸ cells, 90% of which was assayed as diplasmalogen and 10% as diacyl PE. No monoplasmalogen could be detected. The presence of diplasmalogen as the major component of PE was given further support from infrared and proton nuclear magnetic resonance (¹H-NMR) spectroscopy, which showed the presence of O-1′-alkenyl substituents but near absence of O-acyl substituents. The phosphatidylcholine (PC) content of the cells was 104±5 μ/10⁸ cells, of which 50% was monoplasmalogen with the 1′-alkenyl group on the 2 position of the glycerol moiety. No diplasmalogen was found in PC. The other phospholipids in rabbit sperm were phosphatidylglycerol (PG), cardiolipin (CL), sphingomyelin (SP) and lysophosphatidylcholine (LPC). Phosphatidylserine (PS) and phosphatidylinositol (PI) were present at the limits of detectability of the TLC method. None of these phospholipids contained plasmalogen. The PE component of rabbit sperm phospholipids appears to differ from that of the other cells in having the previously unreported diplasmalogen as its major constituent.     

Fatty acid composition of subcellular particles from sheep platelets and topological distribution of phosphatidylethanolamine fatty acids in the plasma membrane

The fatty acid composition of individual phospholipids in subcellular fractions of sheep platelets and the asymmetrical distribution of phosphatidylethanolamine (PE) fatty acyl chains across the plasma membrane were examined. The main fatty acids of total lipid extracts were oleic (18∶1; 32–41%), linoleic (18∶2, 10–17%), stearic (18∶0; 13–15%), palmitic (16∶0; 11–15%) and arachidonic (20∶4; 8–12%) acids, with a saturated/unsaturated ratio of about 0.4. Each phospholipid class had a distinct fatty acid pattern. Sphingomyelin (SM) showed the highest degree of saturation (50%), with large proportions of behenic (22∶0), 18∶0 and 16∶0 acids. The main fatty acid in PE, phosphatidylserine (PS) and phosphatidylcholine (PC) was 18∶1n−9. Our findings suggest that fatty acids are asymmetrically distributed between thecholineversus the non-choline phospholipids, and also between plasma membranes and intracellular membranes. The transbilayer distribution of PE fatty acids in plasma membranes from non-stimulated sheep platelets was investigated using trinitrobenzenesulfonic acid (TNBS). A significant degree of asymmetry was found, which is a new observation in a non-polar cell. The PE molecules from the inner monolayer contained higher amounts of 18∶2 and significantly less 18∶1 and 20∶5 than those found in the outer monolayer, although no major differences were detected in the transbilayer distribution of total unsaturatedversus saturated PE acyl chains.     

Glyceride structure ofCardamine impatiens L. Seed oil

A group of unusual triglycerides, in which one of the acyl groups is a vicinal dihydroxy acid with one of the hydroxyl groups acetylated, has been isolated fromCardamine impatiens L. (Cruciferae) seed oil. Hydrolysis of these triglycerides with castor bean lipase facilitated isolation and identification of a mixture of C₁₈, C₂₀, C₂₂, and C₂₄ hydroxy acetoxy fatty acids. Pancreatic lipase hydrolysis data revealed that these monoacetylated dihydroxy acid residues are esterified exclusively with one of the α-positions of the glycerol moiety. The remaining acyl groups are comprised of ordinary C₁₈ unsaturated acids (which occupy 98% of the β-position), palmitic acid, and C₂₀, C₂₂, and C₂₄ monoenoic fatty acids. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Lipidic characterization of full-grown amphibian oocytes and their plasma membrane-enriched fractions

The content and composition of neutral lipids and phosphoglycerides from full-grown prophase-arrestedBufo arenarum Hensel oocytes and from their ghost preparations were studied. The ghosts obtained are highly enriched in plasma membrane as suggested by the activity of 5′-nucleotidase, a marker enzyme, and the level of typical membrane components such as sphingomyelin, phosphatidylserine (PS), phosphatidylinositol (PI), and phosphatidic acid. In whole oocytes, triacylglyceride (TAG) comprises about 60% of the total lipids followed by phosphatidylcholine (PC), cholesterol, and phosphatidylethanolamine (PE). TAG and diacylglycerides have a similar unsaturation index. PC and PE account for about 80% of the phosphoglycerides in the whole oocyte and in their plasma membrane-enriched fractions. Arachidonic acid (20∶4n−6), 18∶0, and 16∶0 make up about 80 mol% of the total fatty acids in Pl in whole oocytes and ghost fractions. The unsaturation index in PS is higher in intact oocytes than in ghost preparations, probably owing to the significant amount of 20∶4n−6 which comprises 23 mol% of the total fatty acids in whole oocytes. The fatty acid profile in phosphatidic acid from whole oocytes is rather different from that in ghosts. Sphingomyelin contains mainly saturated and monounsaturated fatty acids, 24∶1 being the principal very long chain unsaturated fatty acid in both oocytes and ghosts.     

Thyroid control over biomembranes: VI. Lipids in liver mitochondria and microsomes of hypothyroid rats

The lipids of liver mitochondria prepared from normal rats and from rats made hypothyroid by thyroidectomy and injection with¹³¹INa contained similar amounts, per mg protein, of total lipids, phospholipids, neutral lipids and lipid phosphorus. Hypothyroidism caused a doubling of the relative amounts of mitochondrial cardiolipins (CL; to 20.5% of the phospholipid P) and an accompanying trend (although statistically not significant) toward decreased amounts of both phosphatidylcholines (PC) and phosphatidylserines (PS), with phosphatidylethanolamines (PE) remaining unchanged. The pattern of elevated 18∶2 fatty acyl content and depleted 20∶4 acyl groups of the mitochondrial phospholipids of hypothyroid preparations was reflected to varying degrees in the resolved phospholipids, with PC showing greater degrees of abnormality than PE, and CL showing none. Hypothyroidism produced the same abnormal pattern of fatty acyl distributions in liver microsomal total lipids as was found in the mitochondria. Hypothyroid rats, when killed 6 hr after injection of [1-¹⁴C] labeled linoleate, showed the following abnormalities: the liver incorporated less label into lipids, and converted 18∶2 not exclusively to 20∶4 (as normals do) but instead incorporated the label mainly into saturated fatty acids. These data, together with the known decrease in β-oxidation, suggest that hypothyroidism involves possible defective step(s) in the conversion of 18∶2 to 20∶4. These studies were initiated during a leave at the University of California, Los Angeles.