Method for hydrolysis and isolation of plasmalogen-bound fatty aldehydes

Biosynthesis and metabolism of 2-iodohexadecanal in cultured dog thyroid cells

2-Iodohexadecanal (2-IHDA) is a major thyroid iodolipid. It mimics the main regulatory effects of iodide on thyroid metabolism: inhibition of H2O2 production and of adenylyl cyclase. The biosynthesis of 2-IHDA and its metabolism have been investigated in cultured dog thyroid cells maintained in a differentiated state by forskolin. Incubation of these cells with [9,10-3H]hexadecan-1-ol or [9,10-3H]palmitic acid labeled several phospholipids, but [9, 10-3H]hexadecan-1-ol was selectively incorporated into plasmenylethanolamine. In the presence of an exogenous H2O2 generating system (glucose oxidase), iodide induced the production of [9,10-3H]2-IHDA from [9,10-3H]hexadecan-1-ol-labeled cells but not from [9,10-3H]palmitic acid-labeled cells. 2-IHDA was also generated during the lactoperoxidase-catalyzed iodination of brain and heart plasmalogens, and of ethyl hexadec-1-enyl ether, a synthetic vinyl ether-containing compound. Taken together, these results show that thyroid 2-IHDA is derived from plasmenylethanolamine via an attack of reactive iodine on the vinyl ether group. 2-Iodohexadecan-1-ol (2-IHDO) was also detected in these studies; it was formed later than 2-IHDA, and thyroid cells converted exogenous 2-IHDA into 2-IHDO in a time-dependent way. The ratio of 2-IHDO/2-IHDA increased with H2O2 production and decreased as a function of iodide concentration. An aldehyde-reducing activity was detected in subcellular fractions of the horse thyroid. No formation of 2-iodohexadecanoic acid could be detected. Reduction into the biologically inactive 2-IHDO is thus a major metabolic pathway of 2-IHDA in dog thyrocytes.

Separation of the molecular species of diacyl and alkenylacyl subclasses of the methyl ester of dinitrophenylethanolamine glycerophospholipid by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) procedure for the separation of the molecular species of alkenylacyl and diacyl subclasses after the derivatization of ethanolamine glycero-phospholipids (EGP) to the methyl ester of the dinitrophenylated lipids is described. Methyl esters of dinitrophenylethanolamine glycerophospholipids were first separated into alkenylacyl, alkylacyl and diacyl subclasses by thin-layer chromatography, then each subclass was separated into individual molecular species by reversed-phase HPLC. By converting the EGP into UV-absorbing derivatives, it proved possible to utilize the specificity of spectrophotometric detection for the determination of the individual molecular species. Alkenylacyl and diacyl derivatives were resolved into fifteen to twenty different species in a single HPLC run. The method should facilitate studies on the metabolism of the polar head group of both molecular species of alkenylacyl and diacyl glycerophosphoethanolamine in a variety of tissues using radioactive precursors.

Analysis of platelet phospholipids by high performance liquid chromatography. II--Studies on hitherto unknown peak of phospholipid of human platelets

With our proposed method to analyze platelet phospholipids, utilizing a normal phase high performance liquid chromatography (HPLC), it was able to quantify the amount of major platelet phospholipids (Thromb. Res. 36, 335-344, 1984). A prominent peak of unknown nature (PX) was identified close to the peak of phosphatidylcholine in the HPLC analysis of platelet phospholipids, and the attempts were made to elucidate the nature of PX. By applying several additional authentic phospholipids and those treated by acids on both the HPLC and thin layer chromatography, it was concluded that the major component of PX is 1-lyso phosphatidylethanolamine plasmalogen (PEP), artificially degraded from PEP by the acidic HPLC solvent system. No further degradation of 1-lyso PEP was observed and the absorbance of possibly co-migrated 2-lyso PE in activated platelets was negligible because it was devoid of C-2 double bonds sensitive to the absorbance used in the assay. Therefore, the relative amount of PEP may be detected based on the number of double bonds in platelet PEP. The amount of PEP thus measured was significantly decreased in thrombin-stimulated platelets, suggesting a possible participation of PEP in stimulus-linked platelet reaction.

Metabolism of radiolabelled chylomicron lipids in intact and hepatectomized rats

Intact rats removed more radiolabelled triacylglycerol, cholesterol, and cholesterol ester but not phosphatidylcholine (PC) in the first 6 min than hepatectomized rats. There was no difference between intact and hepatectomized rats in the transfer of radiolabelled chylomicron lipids to other lipoproteins. Specific radioactivity measurements demonstrated a net transfer of PC (intact and hepatectomized rats) and unesterified cholesterol (intact rats only) onto both the low density lipoprotein/high density lipoprotein-1 (LDL/HDL1) and HDL2 fractions. [3H]Fatty acids were rapidly incorporated into blood cell phospholipids and into HDL and LDL cholesterol esters of both intact and hepatectomized rats. Substantial rearrangements of [3H]palmitate occurred during lipid uptake by liver.

Synthesis and properties of 35S, 14C and 3H labeled S-alkyl glycerol ethers and derivatives

Radioactive S-alkyl glycerol ethers have been synthesized with 35S, 14C and 3H labels as well as 3H/35S double labels. The synthesized compounds were converted to various derivatives which can serve to characterize the S-alkyl glycerol ethers. These included the isopropylidene derivative, oxidation with periodate to the aldehyde followed by reduction with LiAlH4 to the alcohol, and reaction of the alcohol with acetic anhydride to form the acetate derivative. Chemical analysis, IR, NMR, zonal TLC profile scans and GLC showed all the products to be greater than 99% pure. The GLC behavior of the aldehyde and acetate derivatives of both S-alkyl glycerol ethers and O-alkyl glycerol ethers on EGSS-X was compared.