Use of t-butyldimethylchlorosilane/imidazole reagent for identification of molecular species of phospholipids by gas-liquid chromatography mass spectrometry

Lipid profiling of rat peritoneal surface layers by online normal- and reversed-phase 2D LC QToF-MS

An online, two-dimensional (2D) liquid chromatography (LC) quadrupole time-of-flight mass spectrometry (QToF-MS) method was developed for lipid profiling of rat peritoneal surface layers, in which the lipid classes and species could be simultaneously separated in one injection with a significantly increased sensitivity. Different lipid classes were separated on a normal-phase column in the first dimension and lipid molecular species were separated on a reversed-phase column in the second dimension, so that the ion suppression effects were reduced while the detection sensitivity was improved. Identified were 721 endogenous lipid species from 12 lipid classes, in which 415 structures were confirmed using tandem mass spectra, and the other 306 lipid molecular species were identified by accurate masses. The linearity, limit of detection, and repeatability were all satisfactory. The method was applied to the investigation of the lipid changes in rat peritoneal surface layer after peritoneal dialysis, and 32 potential lipid biomarkers were identified, as their concentrations in the dosed group were 2.2-12.5 times of those in the control group. The results revealed that this 2D LC-MS system was a promising tool for lipid profiling of complex biological samples.

Derivatization of phospholipids

Phospholipids are major components of biological membranes. Without chemical derivatization, it is difficult to identify and quantitate phospholipids in biological samples. Chemical derivatization can improve both the selectivity and sensitivity of the analytes. This paper gives a full review, through March, 2002, of derivatization methods used for phospholipids in HPLC, CE and GC as well as the spray reagent used for TLC in the early days.

Derivatization in mass spectrometry--1. Silylation

This is the first of a series of reviews on the application of derivatization in mass spectrometry. A description is given of advances in silylation as a powerful tool used for increasing the volatility, thermal and thermo-catalytic stability, and chromatographic mobility of polar and unstable organic compounds. In addition to chemical aspects of silylation, mass spectral properties of silyl derivatives useful for structure determination and quantitation of various organic and biologically-active compounds, mainly by GC/MS, are described. Practically all tested and widely used silylating agents are described. The role of comprehensive libraries containing reference mass spectra for various silyl derivatives and search systems in structure determination is emphasized. Applications of silylation for particular analyses are summarised.

Mass spectrometric analysis of platelet-activating factor after isolation by solid-phase extraction and direct derivatization with pentafluorobenzoic anhydride

Platelet-activating factor is the term used to denote a class of extremely potent lipid mediators that consist predominantly of 1-O-alkyl- and 1-O-acyl-2-acetyl-sn-glycero-3-phosphocholines. A method has been devised for rapid isolation of these acetylated phospholipids by solid-phase extraction prior to direct derivatization with pentafluorobenzoic anhydride and analysis by gas chromatography (GC)/electron-capture mass spectrometry. Recovery through the entire method (lipid isolation, derivatization, and purification) typically ranged from 70% to 85%. Using the direct derivatization procedure described here, the practical limit of detection for each of the standard alkyl- and acyl-platelet-activating factor homologs was 1 fmol injected into the GC. Results from the application of the method to the analysis of alkyl and acyl homologs of platelet-activating factor isolated from stimulated human umbilical vein endothelial cells are presented, exhibiting excellent accuracy and precision for a wide range of tissue levels of this class of potent autacoids.

General strategies in chromatographic analysis of lipids

Lipid extracts of natural sources contain a large number of lipid classes and molecular species. Completely reproducible samples are obtained only with great care and skill. Analytical methods other than chromatography and/or mass spectrometry are of little use for resolution and identification of lipid molecules even in simple mixtures. The analytical information desired governs the selection of the chromatographic and mass spectrometric method, which determine the sample preparation and derivative needed. Usually a combination of chromatographic methods is necessary to identify specific species of lipids. The recent development of soft ionization techniques, that are readily interfaced with mass spectrometers, have greatly simplified the sample preparation and have largely eliminated the need for derivatization. Because these techniques require expensive equipment and dedicated operators, the methods selected must be consistent with the true analytical needs and the available resources. Although personal preference cannot be eliminated entirely, the general strategies outlined below should help to reduce the number of possibilities facing a lipid analyst to a few practical choices.

Evidence for production of platelet-activating factor by yeast Saccharomyces cerevisiae cells

Various yeast strains were screened for platelet-activating factor (PAF) production. High PAF production was found mainly in the strains of Saccharomyces genus. Yeast PAF showed a typical platelet aggregation pattern, which was inhibited by specific PAF antagonists, such as CV-3988, CV-6209 and L-652731. The main molecular species of yeast PAF were identified as 1-palmitoleoyl-, -palmitoyl-, -oleoyl- and -stearoyl-2-acetyl-sn-glycero-3-phosphocholines (16:1, 16:0, 18:1 and 18:0 acylPAFs) and 1-hexadecenyl- and hexadecyl-2-acetyl-sn-glycero-3-phosphocholines (16:1 and 16:0 PAFs), by mass spectrometry. PAF formation in yeast cells increased at the middle stationary phase of growth.

Differential electron capture mass spectral response of pentafluorobenzoyl derivatives of platelet activating factor alkyl chain homologs

The electron capture mass spectrometric response of pentafluorobenzoyl ester derivatives of platelet-activating factor alkyl chain homologs has been found to be inversely proportional to their alkyl chain length. This phenomenon was observed when either the gas chromatograph or direct insertion probe was utilized for sample introduction. A similar differential response was also obtained for a series of fatty alcohols, analyzed as pentafluorobenzoyl esters. These studies demonstrate that multiple standard curves must be prepared for analysis of platelet-activating factor and related lipids in order to obtain accurate quantification.

Defective glomerular [3H]lysoPAF metabolism in the autologous phase of rabbit nephrotoxic nephritis

Glomerular infiltration of blood-derived mononuclear cells contributes to the glomerular injury in the autologous phase of nephrotoxic nephritis (NTN). LysoPAF has recently been shown to be chemotactic for human monocytes, thus its accumulation might account for monocyte recruitment. We investigated [3H]lysoPAF metabolism in isolated glomeruli from normal and NTN rabbits studied both in the heterologous and in the autologous phases of the disease. [3H]lysoPAF was converted to [3H]1-O-alkyl-glycerol and [3H]1-O-alkyl-2-acyl-GPC by phospholipase C and acyltransferase, respectively, both in normal and NTN glomeruli. Glomerular metabolism of [3H]lysoPAF was normal during the heterologous phase of NTN. By contrast, in isolated glomeruli from NTN rabbits studied in the autologous phase of the disease, a significantly lower [3H]lysoPAF degradation occurred with respect to normal ones. This defective degradation resulted in a significantly reduced formation of [3H]1-O-alkyl-glycerol. The apparent Km for enzymatic conversion of [3H]lysoPAF to [3H]1-O-alkyl-glycerol, determined at 15 minutes as a function of [3H]lysoPAF concentration, was doubled in glomeruli from rabbits studied in the autologous phase of NTN as compared to normal ones, while Vmax values were similar in the two groups. These results show a defective glomerular lysoPAF degradation in the autologous phase of NTN, likely due to a decreased affinity of phospholipase C to lysoPAF. Altered lysoPAF metabolism results in glomerular accumulation of lysoPAF in the autologous phase of NTN, as shown by significantly higher levels of lysoPAF measured in nephritic glomeruli as compared to normal ones.

Phospholipids from the free-living nematode Caenorhabditis elegans

The phospholipid and the fatty chain compositions of diacyl, alkylacyl and alkenylacyl glycerophospholipids of the free-living nematode, Caenorhabditis elegans, were investigated. The phospholipids were comprised of 54.5% ethanolamine glycerophospholipid (EGP), 32.3% choline glycerophospholipid (CGP), 8.1% sphingomyelin and 5.1% others. The most abundant fatty acid in CGP was eicosapentaenoic acid (20:5n-3). The fatty acids in CGP were more unsaturated than those in EGP. Alkenylacyl and alkylacyl subclasses accounted for 1.0 and 2.6%, respectively, of CGP and 14.0 and 19.6%, respectively, of EGP. At least 80% of the alkenyl and alkyl groups were 18:0 chains and the remaining were odd numbered chains. The potential presence of platelet-activating factor (PAF) was examined by bioassay, but PAF-like activity was not detected in the extracts of this nematode.

Platelet-activating factor detected in bronchoalveolar lavage fluids from an asthmatic patient

It recently has been recognized that platelet-activating factor (PAF) may be a mediator of asthma exacerbation. We had the opportunity to analyze bronchoalveolar lavage fluids from an asthmatic infant, which were characterized by neutrophil infiltration. The patient's lungs were washed on three occasions with saline during asthmatic attacks. PAF was found in each case on the basis of its ability to cause the immediate aggregation of washed rabbit platelets. The PAF detected was equivalent to 1-1.4 pmol of 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, three quarters of which were recovered in cell-associated form. By contrast, we did not detect PAF in bronchoalveolar exudates from patients with laryngeal stenosis or with respiratory distress syndrome. LysoPAF, the direct precursor as well as initial metabolite of PAF, was also analyzed after being converted to PAF by acetylation. There was a wide variation in the amount of lysoPAF present in individual patients, suggesting that lysoPAF levels cannot be taken as an indicator for the presence of PAF.

Molecular heterogeneity of platelet-activating factor (PAF) in rat glandular stomach determined by gas chromatography/mass spectrometry. PAF molecular species changes upon water-immersion stress

The molecular heterogeneity of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (alkylacetyl-GPC) and 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (acylacetyl-GPC) in normal rat glandular stomach was studied by gas chromatography/mass spectrometry (GC/MS) and tandem mass spectrometry. The percentage compositions of the molecular species of 1-alkyl-2-acetyl-GPC and 1-acyl-2-acetyl-GPC in the antrum were, respectively, 1-alkyl [16:0 (34%) and 18:0 (66%)]-2-acetyl-GPC and 1-acyl [16:0 (60%), 18:0 (14%) and 18:1 (26%)]-2-acetyl-GPC. The alkyl chain composition of 1-alkyl-2-acetyl-GPC was quite different from that of 1-alkyl-2-acyl-GPC in both the antrum and corpus, demonstrating a high degree of selectivity of alkyl chain utilization in PAF biosynthesis. The amount of 1-acyl-2-acetyl-GPC was much greater than that of 1-alkyl-2-acetyl-GPC. The molecular heterogeneity of 1-alkyl-2-acetyl-GPC and 1-acyl-2-acetyl-GPC in the corpus was similar to that in the antrum. Water-immersion stress affected not only the amount of 1-alkyl-2-acetyl-GPC and 1-acyl-2-acetyl-GPC, but also their molecular heterogeneity in the antrum and corpus. Whereas the amounts of 1-hexadecyl-2-acetyl-GPC and 1-acyl [16:0, 18:0 and 18:1]-2-acetyl-GPC decreased markedly (to less than one-fifth) in the antrum after such stress for 1 hr, the amount of 1-octadecyl-2-acetyl-GPC increased markedly (up to 4-fold) in the corpus and severe lesions were observed after stress for 7 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of 17 beta-estradiol on PAF and prostaglandin levels in oophorectomized rat uterus

The effects of 17 beta-estradiol on the levels of platelet-activating factor (PAF) and prostaglandins and their precursor phospholipid in the uterus of oophorectomized rats were studied. Oophorectomy results in the decrease in the uterine PAF level to one-third of that in natural estrus. This level was recovered by subcutaneous administration of 17 beta-estradiol. The level of uterine phospholipids, which are rich in arachidonic acid, was significantly decreased by estradiol treatment. More arachidonate-PC was depleted than arachidonate-PE. The molecular structure was confirmed by gas chromatography-mass spectrometry. The amount of PGF2 alpha in the oophorectomized uterine tissue was 10-times that of PAF, but like the latter, increased 3-4 times on estradiol treatment. The chemical structures of PAF and PGF2 alpha formed on estradiol treatment were confirmed by mass spectrometry. The present data strongly suggest a correlation between the formations of PAF and PGF2 alpha, and indicate that estradiol may regulate the physiological formations of PAF and PGs in non-pregnant rat uterus.

Analysis of platelet-activating factor by gas chromatography-mass spectrometry: low-energy electron impact of the corresponding 3-acetyl-2-tert.-butyldimethylsilyl derivative

A method for the analysis of platelet-activating factor in platelets employing gas chromatography and selected-ion monitoring mass spectrometry with low-energy electron impact and stable isotope dilution was developed. The procedure involved Bligh and Dyer extraction of the sample followed by thin-layer chromatographic purification. Platelet-activating factor is successively hydrolysed to the corresponding 2-acetyl-1-O-alkylglycerol by digestion with phospholipase C, and the product is allowed to isomerize to the more thermodynamically stable 3-acetyl-1-O-alkylglycerol before column purification and derivatization of the free OH with tert.-butyldimethylchlorosaline-imidazole. This reagent is of common use in platelet-activating factor derivatization, but is made to react with 2-acetyl instead of 3-acetyl isomer. The advantages of using the latter for the final derivatization are discussed and this method is compared with others currently available for gas chromatographic-mass spectrometric analysis of platelet-activating factor.

Characterization of phosphatidylcholines in rabbit lung lavage fluid by positive and negative ion fast-atom bombardment mass spectrometry

The relative distribution of intact diacylphosphatidylcholine species isolated from the lung lavage fluid of rabbits has been investigated by positive ion fast-atom bombardment (FAB) mass spectrometry. Two different isolation/purification methods were applied and evaluated prior to mass spectrometric analysis. The first method consisted of a Bligh and Dyer extraction of the lung lavage fluid followed by isocratic high-performance liquid chromatographic (HPLC) separation. In the second method a thin-layer chromatographic purification step was introduced between the extraction procedure and the HPLC separation. Further, the FAB matrices glycerol and 3-nitrobenzyl alcohol were used, and their influence on the diacylphosphatidylcholine molecular ion species was studied. The Bligh and Dyer extraction followed by the simple HPLC separation was the method of choice to obtain stable, long-lasting protonated molecular ions and diagnostic fragment ions, which permitted the identification of the polar head-group. In combination with 3-nitrobenzyl alcohol as liquid matrix we established a procedure that yielded a fast sample preparation method, a good signal-to-noise ratio for detecting minor species, and reduced formation of [M+H-2H]+ ion species. The relative fatty acid composition of the diacylphosphatidylcholine fractions isolated from rabbit lung lavage fluid was determined by negative ion FAB mass spectrometry using the carboxylate anions. The mass spectrometric results were compared with those acquired by gas chromatographic determination of the fatty acid methyl esters. Close agreement was found between the data obtained by the two independent methods.

Molecular species analysis of phospholipids by negative ion fast atom bombardment mass spectrometry: application of surface precipitation technique

Eight phospholipidic classes from bovine brain cortex and soybean were prepared and purified by preparative high-performance and liquid chromatography, and their molecular species were identified by negative ion fast atom bombardment mass spectrometry using the 'surface precipitation' method. Its main advantages are: (i) clear-cut and abundant diagnostic ions for structural elucidation of the species; (ii) fragments characteristic of the main fatty acids, the polar head-group and the molecule frame in phospholipids; (iii) less background caused by the liquid matrix.

Acyl type platelet-activating factor in normal rat uterus determined by gas chromatography mass spectrometry

1-Fatty acyl-2-acetyl-sn-glycero-3-phosphocholine (1-fatty acyl-2-acetyl GPC, acyl type platelet-activating factor (PAF) was found in normal rat uterus without addition of any exogenous stimuli and identified as 1-palmitoyl, 1-oleoyl and 1-stearoyl species by gas chromatography/mass spectrometry coupled with selected ion monitoring (SIM). The main species was the 1-palmitoyl species. The ions used for SIM were chosen on the basis of the acetyl and fatty acyl moieties and molecular weight. The amount of 1-fatty acyl-2-acetyl GPC was significantly more than that of PAF (1-fatty alkyl-2-acetyl GPC, AGEPC), and the ratio of 1-palmitoyl-2-acetyl GPC to 1-0-hexadecyl-2-acetyl GPC was about 4.5:1 in normal rat uterus.

1-O-hexadec-1'-enyl-2-acetyl-sn-glycero-3-phosphocholine and its biological activity

1-O-Alk-1'-enyl analog of platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, alkylacetyl-GPC) was prepared semi-synthetically from choline plasmalogens of beef heart muscle. The main compound was identified mass spectrometrically as 1-hexadec-1'-enyl-2-acetyl-sn-glycero-3-phosphocholine (16:O alk-1'-enylacetyl-GPC, 16:O vinyl form of PAF) and its platelet aggregation activity was about one-fifth of that of the corresponding 16:O alkylacetyl-GPC. The irreversible platelet aggregation activity induced by 5X10(-10) M 16:O alk-1'-enylacetyl-GPC was completely inhibited by 5X10(-7) M CV-3988 and 1X10(-7) M L-652, 731, specific PAF antagonists, and more than 99% of the activity was also lost by acid treatment. The hydrogenated product, alkylacetyl analog, showed quite same activity as that of authentic 16:O alkylacetyl-GPC. The platelets desensitized with 16:O alkylacetyl-GPC and with 16:O alk-1'-enylacetyl-GPC were not aggregated with 5X10(-10) M 16:O alk-1'-enylacetyl-GPC, suggesting that alk-1'-enylacetyl-GPC occupied the same receptor site of alkylacetyl-GPC.

Fast atom bombardment and tandem mass spectrometry of phosphatidylserine and phosphatidylcholine

Fast atom bombardment (FAB) desorption of phosphatidylserine and various phosphatidylcholines produces a limited number of very informative negative ions. Especially significant is the formation of (M-H)- ions for phosphatidylserine, a compound which does not yield informative high mass ions by other ionization methods. Phosphatidylcholines do not yield (M-H)- ions but instead produce three characteristic high mass ions, (M-CH+3)-, [M-HN(CH3)+3]- and [M-HN(CH3)+3-C2H2]-. Both classes of lipids also yield anions attributed to the carboxylate components of these complex lipids. FAB desorption in combination with collisional activation allows for characterization of fragmentation and determination of structural features. Collisional activation of the carboxylate anion fragments from the complex lipids is especially informative. Structural characterization of the fatty acid chain can be achieved as the released saturated carboxylate anions undergo a highly specific 1,4-elimination of H2, which results in the losses of the elements of CH4, C2H6, C3H8 . . . in a fashion entirely consistent with the chemistry of carboxylate anions desorbed from free fatty acids. These CnH2n + 2 losses begin at the alkyl terminus and progress along the entire alkyl chain. Modified fatty acids undergo a similar fragmentation; however, the modification affects the series of CnH2n + 2 losses in a manner which permits determining the type of modification and its location on the fatty acid chain.

Platelet-activating factor in normal rat uterus

Platelet-activating factor (PAF) was found in normal rat uterus and identified as 1-0-hexadecyl/octadecenyl-2-acetyl-sn-glycero-3-phosphocholine. PAF was purified by several successive chromatographic procedures. It showed platelet aggregating activity, which was inhibited by CV 3988, and had no effect on platelets desensitized with 1-0-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine. The tert-butyldimethyl-silylderivative of 1-0-alkyl-2-acetyl-sn-glycerol, which was obtained by hydrolysis of uterine PAF with phospholipase C, was analyzed by gas chromatography-mass spectrometry. One rat uterus contained approximately 21.3 ng of 1-0-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine. This is the first report of the occurrence of a significant amount of PAF in a normal animal tissue.

Measurement of sub-picogram quantities of platelet activating factor (AGEPC) by gas chromatography/negative ion chemical ionization mass spectrometry

A very sensitive method of 1-O-alkyl-2-acetyl-sn-glycerophosphocholine (platelet activating factor) quantitation is described. 1-O-Alkyl-2-acetyl-sn-glycerophosphocholine is converted to 1-O-alkyl-2-acetylglycerol by treating with phospholipase-C which is in turn acylated with pentaflurobenzoyl chloride. The resulting diglyceryl ester of pentafluorobenzene is analysed by gas chromatography/negative ion chemical ionization mass spectrometry. With methane as the reagent gas the pentafluorobenzoyl acyl derivative yields mainly the molecular anion ([M]-.) representing more than 92% of the total ion current. Deuterium-labeled 1-O-hexadecyl-2-(2H3)acetyl-sn-glycerophosphocholine is used as the internal standard for quantitation. The standard curves are linear and typically have a correlation coefficient of greater than 0.999. Using 1 pg of the deuterium-labeled internal standard, quantities as low as 100 fg are measured.

Fast atom bombardment analysis of arachidonic acid-containing phosphatidylcholine molecular species

Fast atom bombardment (FAB) mass spectrometry was evaluated as a means for the characterization of molecular species of glycerophosphocholines (GPC) from HL60 cells. Previous reports of phospholipid molecular species analysis have suggested that several inherent problems with FAB could limit its analytical usefulness in such an application. The GPC-related secondary ions produced by the FAB experiment were found to be dependent on the matrix employed. Triethanolamine was found to minimize mass-related discrimination in ion emission when mixtures were studied; and furthermore, this matrix maintained 60% maximal ion current after 12 minutes as compared to a glycerol matrix which diminished to 10% maximal ion current. Using triethanolamine, the major GPC species in HL60 cells prelabeled with (2H8) arachidonic acid were found to be 16:0a16:1, 16:0e/18:1, 16:0a/18:1, 18:1a/18:1 and 18:0a/18:1. It was possible to identify the minor GPC species containing arachidonic acid only after partial purification by reverse-phase high-performance liquid chromatography. Comparison of the 2H8/2H0 enrichment data estimated by FAB with data obtained by gas chromatographic/mass spectral analysis of arachidonic acid following GPC hydrolysis revealed that the precision of FAB was less precise than gas chromatography/mass spectrometry. Yet the FAB technique did allow the observation of one unexpected molecular species (18:1a/20:4) due to the fact that the GPC was not degraded to simpler species prior to analysis. In this respect, the two strategies of molecular species analysis complement each other.

Evidence for production of 1-acyl-2-acetyl-sn-glyceryl-3-phosphorylcholine concomitantly with platelet-activating factor

The presence of 1-acyl-2-acetyl-sn-glyceryl-3-phosphorylcholine in a sample of platelet-activating factor from stimulated rabbit neutrophils was demonstrated by a gas-liquid chromatography/mass spectrometry technique coupled with selected ion monitoring. The ions chosen for identification were those of acetyl and long-chain acyl moieties and molecular weight. Species containing palmitic, oleic and stearic acids were detected. A good correlation was observed between the productions of 1-acyl-2-acetyl-sn-glyceryl-3-phosphorylcholine and 1-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine by neutrophils stimulated with ionophore A23187.

Generation of acetyl glyceryl ether phosphorylcholine from the rat skin and muscle tissues stimulated by moxibustion

Platelet-activating factor was obtained from the rat skin and muscle tissues which were stimulated by moxibustion. It showed a typical aggregation pattern on interaction with washed rabbit platelets but when it was treated with phospholipases A2 and C, and CV 3988 the aggregation activity was lost. Platelet-activating factor was hydrolysed with phospholipase C and the resulting lipid product was converted to the tert-butyldimethylsilyl derivative. After purification by thin layer chromatography, the ether type of derivative was analysed by a selected ion monitoring technique of gas chromatography-mass spectrometry. 1-0-Hexadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine only was identified.

Structural identification of platelet activating factor in psoriatic scale

Platelet activating factor was isolated from the lesional scale of psoriatic patients using the method described by Bligh and Dyer (8). The extract was subjected to thin layer chromatography, and the region of the plate co-migrating with platelet activating factor removed. A portion of each sample was assayed for aggregating activity using washed guinea-pig platelets and the remainder treated with phospholipase C, derivatised, and subjected to reversed phase high performance liquid chromatography. Fractions were analysed for platelet activating factor using capillary gas chromatography-mass spectrometry. Nanogram quantities of platelet activating factor were recovered from 100 mg scale and both the C16 and C18 alkyl substituents were present in the ratio 3:1, C16:C18.

Studies on molecular species of choline and ethanolamine glycerophospholipids obtained from rat brain myelin and synaptosomes by gas-liquid chromatography mass spectrometry

By converting to t-butyldimethylsilyl derivatives, molecular species of ethanolamine glycerophospholipid including both 1,2-diacyl and 1-alk-1'-enyl-2-acyl (plasmalogen) types were able to be analysed by a gas chromatography mass spectrometry selected ion monitoring technique. The samples analysed were ethanolamine glycerophospholipid and also choline glycerophospholipid obtained from myelin and synaptosomes of rat brain, both of which are characteristic subcellular organella of the nervous system. Main molecular species of ethanolamine glycerophospholipid were as follows: in myelin as 1,2-diacyl type, 36:1 (mainly 18:0/18:1), and as 1-alk-1'-enyl-2-acyl type, 34:2 (mainly vinyl 16:0/18:1), 36:2 (mainly vinyl 18:0/18:1) and 36:3 (mainly vinyl 18:1/18:1), whereas in synaptosomes as 1,2-diacyl type 36:1 (mainly 18:0/18:1), 38:4 (mainly 18:0/20:4) and 40:6 (18:0/22:6), and as 1-alk-1'-enyl-2-acyl type 34:2 (mainly vinyl 16:0/18:1), 36:2 (mainly vinyl 18:0/18:1), and 36:3 (mainly vinyl 18:1/18:1). The molecular species of choline glycerophospholipid consisted almost entirely of 1,2-diacyl type and they were in myelin 34:1 (mainly 16:0/18:1), 36:1 (mainly 18:0/18:1) and 36:2 (mainly 18:1/18:1), whereas in synaptosomes 32:0 (mainly 16:0/16:0), 34:0 (16:0/18:0), 34:1 (mainly 16:0/18:1) and 36:1 (mainly 18:0/18:1). In myelin as 1-alkyl-2-acyl type, 34:1 (1-hexadectl-2-octadecenoyl) was present at about 7%.

Analysis of molecular species of phospholipids by field desorption mass spectrometry

Various glycerophospholipids including their trimethylsilyl and t-butyldimethylsilyl derivatives and cerebroside were analysed by field desorption mass spectrometry with a silicon emitter. Choline glycerophospholipids with diacyl residues and also alk-1'-enyl and acyl residues gave the readily interpretable field desorption mass spectra in which a sodium cluster ion [M+NA]+ was a base peak. As to phosphatidylethanolamine and cerebroside, a protonated molecular ion [M+H+]+ was a base peak. The TMS and TBDMS derivatives gave a molecular ion [M]+. The field desorption analysis of natural phospholipids from myelin was carried out in comparison with the gas chromatographic mass spectrometric analysis.

Phospholipid metabolism of dog liver under hypoxic conditions induced by ligation of the hepatic artery

Ischemic hypoxic liver was induced in dogs by ligation of the hepatic artery. About 67% of the dogs died of liver necrosis within 1 or 2 days (severe cases), and the rest survived (mild cases). In the severe cases, the decreases in the contents of total lipids, phospholipids and proteins of the liver after 24 h were 24, 46 and 12%, respectively, of the original values. The marked decrease in phospholipids was due to decreases in the microsomal and mitochondrial fractions. In the mild cases, similar but smaller decreases occurred and decrease of phospholipids occurred only in the microsomal fraction. The main phospholipids were choline and ethanolamine glycerophospholipids, and their molecular species were analyzed. In the severe cases, ligation resulted in relative increases in mono- and diene species and a decrease in polyene species. No increase in phospholipase activity was found at various times after ligation of the hepatic artery. Penicillin-treated dogs all survived and showed little decrease in liver phospholipids.