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Biomedical subjects

D J Hanahan

Publications and source records attributed to D J Hanahan.

At least 73 records · Page 4Linked to original sources
PubMed1985

Phospholipid and detergent effects on (Ca2+ + Mg2+)ATPase purified from human erythrocytes.

(Ca2+ + Mg2+)ATPase (EC 3.6.1.3) was solubilized from human erythrocyte membranes by detergent extraction with Triton N-101 (0.5 mg/mg membrane protein) and purified by calmodulin affinity chromatography. ATPase activity was assayed in mixtures of Triton N-101 and phospholipid, without reconstitution into bilayer vesicles. At low levels of phospholipid (5 micrograms/ml), the ATPase activity was highly sensitive to the detergent concentration, with maximal activity occurring at or near the critical micelle concentration of the detergent. With increased amounts of phospholipid (50 micrograms/ml), detergent concentrations greater than the critical micelle concentration were required for maximal activity. Detergent alone did not support ATPase activity. Sonicated phospholipid in the form of vesicles was equally ineffective. Activity seemed to be dependent on the presence of detergent/phospholipid mixed micelles. The acidic phospholipids, phosphatidylserine and phosphatidylinositol, as well as the commercial phospholipid preparation, Asolectin, gave activities five to eight times greater than the same amount of phosphatidylcholine. Mixtures of phosphatidylserine and phosphatidylcholine produced intermediate ATPase activities, with the maximal value dependent on the phosphatidylserine concentration. Addition of phosphatidylcholine to fixed concentrations of phosphatidylserine caused a rise in activity that was independent of the ratio of the two phospholipids or the total phospholipid concentration. Phosphatidylcholine may therefore be irreplaceable for some aspect of ATPase function. The number of phospholipid molecules present in mixed micelles at maximal ATPase activity was calculated to be near 50. This value implied that the hydrophobic surface of the ATPase molecule must be completely coated by a single layer of phospholipid molecules for maximum activity to occur.

Ca(2+) Mg(2+)-ATPase↗
PubMed1985

Stimulation of (Ca2+ + Mg2+)-ATPase activity in human erythrocyte membranes by synthetic lysophosphatidic acids and lysophosphatidylcholines. Effects of chain length and degree of unsaturation of the fatty acid groups.

Synthetic lysophosphatidic acids and lysophosphatidylcholines were examined for their effects on the (Ca2+ + Mg2+)-ATPase of human erythrocyte membranes. Addition of these compounds to erythrocyte ghosts caused significant changes in ATPase activity. The degree of unsaturation and the length of the sn-1 long chain hydrocarbon moiety were both contributing factors. All lysophosphatidic acids tested stimulated (Ca2+ + Mg2+)-ATPase activity. Of the species having a saturated acyl group, the most active was the myristoyl derivative. Linoleoyllysophosphatidic acid was the most potent of the unsaturated species. Saturated lysophosphatidylcholines with a short chain fatty acyl group (C10 to C14) exhibited only a moderate stimulatory activity, whereas the longer chain homologues, i.e., C16 and C18 were inhibitory at high concentrations. On the other hand, unsaturated lysophosphatidylcholines had stimulatory activities comparable to the unsaturated lysophosphatidic acids. These results suggest that the acidic moiety of lysophosphatidic acid is not an important structural determinant for expressing ATPase stimulatory activity in ghosts. Rather the nature of the hydrocarbon chain as well as the lyso structure of these compounds appear most critical under these conditions. The stimulatory effects of lysophosphatidic acids or lysophosphatidylcholines were additive to that induced with calmodulin, suggesting that these lysophospholipids affect the (Ca2+ + Mg2+)-ATPase by a mechanism which is different from that seen with calmodulin.

Adult↗
PubMed1985

Platelet-activating factor: a unique lipid chemical mediator.

Several different laboratories have provided sufficient information to establish platelet-activating factor, or AGEPC, as one of the most potent lipid chemical mediators known to date and one with a particularly broad spectrum of biological activities. The data presented in this chapter strengthen this generalization and show yet another dramatic biochemical effect of this unusual phosphoglyceride. The mechanism by which AGEPC effects glycogenolysis and vasoconstriction remains the subject of an ongoing investigation.

Animals↗
PubMed1985

A novel approach to structure proof of glyceryl ether-containing glycerophospholipids. Base-catalyzed methanolysis of platelet-activating factor (AGEPC) at 60 degrees C.

A novel reaction was explored in which synthetic platelet-activating factor, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC), upon treatment with 1 N NaOH in methanol at 60 degrees C for 20 min, sequentially released the acetyl group, then the choline moiety with concomitant formation of the monomethyl ester of 1-O-alkyl-glycero-phosphoric acid. A mechanism is proposed in which a transient cyclic phosphate intermediate is formed and then attacked by a CH3O moiety to yield a mixture of the sn-2 and sn-3 methyl esters. Proof of structure of the monomethyl ester derivative was achieved through the use of thin-layer chromatography, aluminum oxide chromatography, and examination of the trimethylsilyl derivative of the monomethyl ester by gas-liquid chromatography-mass spectrometry. Replacement of the acyl group on the 2 position with an ethyl or methyl residue completely prevented any attack by 1 N NaOH in methanol at 60 degrees C. Sphingomyelin was not attacked and only acetate removal was noted with 1-O-alkyl-2-acetyl-sn-glycero-3-phosphoethanolamine under similar conditions. The significance of these findings as they relate to the influence of substituents on the chemical and biological reactivity of AGEPC is discussed.

Chromatography, Thin Layer↗
PubMed1984

Partial purification and characterization of a novel Mg2+-dependent ATPase present in the cytosol from human erythrocytes.

Mg2+-ATPase activity was identified in the cytosol of human erythrocytes. A partial purification of this activity was achieved by an initial DEAE-Sephadex column chromatography, followed by gel filtration on Sephadex G-100 and then a second DEAE-Sephadex chromatography procedure. The enzyme appeared in the void volume of the Sephadex G-100 column and was retained on an Amicon XM100A ultrafiltration membrane. The molecular weight of the enzyme was estimated to be 113 000 from SD gels. The above purification protocol yielded an enzyme with an optimal pH between 7.6 and 8.2. The enzyme activity increased linearly between 30 and 44 degrees C. It was stable for several months at -20 degrees C. Magnesium was essential for activity, but the rate attainable with Mn2+ was at least as great as that due to Mg2+. No other divalent cation was able to substitute for Mg2+ or Mn2+. Neither low nor high Ca2+ concentrations significantly affected the enzymatic activity. Substrate specificity studies showed that ATP was the preferred substrate followed by CTP (46% of the rate produced by ATP). Hydrolysis of GTP, UTP, ITP and ADP was less than 10% of the rate seen with ATP. No phosphatase, pyrophosphatase, phosphodiesterase, hexokinase, phosphofructokinase or adenylate cyclase activity could be detected in this enzyme preparation. Calmodulin, which stimulates the (Ca2+ + Mg2+)-ATPase of the human erythrocyte membrane, failed to enhance the Mg2+-ATPase activity. Of considerable interest, the activity of this Mg2+-ATPase was enhanced approximately 5-fold by low concentrations of mercuric ion, p-hydroxymercuribenzoate and DTNB, but was much less sensitive to iodoacetamide.

Adenosine Triphosphatases↗
PubMed1984

Phospholipids as dynamic participants in biological processes.

Phospholipids are described as active biological molecules. Three distinctly different roles are examined. The first centers on protein-lipid interactions and the lipid requirement expressed by certain enzymes. This category is illustrated by two soluble proteins of the blood coagulation scheme, Factor IXa and Factor Xa, and by an integral membrane protein, the (Ca2+ + Mg2+)-ATPase of human erythrocytes. The next two examples depict phospholipids as active participants in membrane-mediated events. In the first of these, termed the phosphoinositide effect, a phospholipid becomes a substrate during membrane signaling, and its products presumably act as second messengers. In the second example, a phospholipid is a signal that, among other reactions, induces the phosphoinositide effect. Here, the phospholipid (platelet activating factor) serves as a lipid chemical mediator. These examples show that phospholipids behave not only as structural molecules but also as dynamic, functionally important components of cells.

Blood Coagulation↗
PubMed1984

Stimulation of glycogenolysis and platelet-activating factor production by heat-aggregated immunoglobulin G in the perfused rat liver.

Infusion of heat-aggregated immunoglobulin G (IgG) into perfused livers from fed rats resulted in a dose-dependent but transient stimulation of hepatic glucose output. Oxygen consumption and lactate production by the liver also were stimulated, while the lactate/pyruvate ratio of the effluent perfusate was increased. Upon return of hepatic glucose output to the basal rate following immune aggregate stimulation, a second infusion of immune aggregate caused little or no increase in glucose output, indicating desensitization of the response. Infusion of immune aggregate into rat livers also resulted in the appearance of platelet-activating factor activity in the effluent perfusate. Synthetic platelet-activating factor or acetylglyceryl ether phosphorylcholine (AGEPC) has been demonstrated to be a potent glycogenolytic agonist in the perfused liver (Buxton, D.B., Shukla, S. D., Hanahan, D. J., and Olson, M.S. (1984) J. Biol. Chem. 259, 1468-1471). The glycogenolytic response of the liver to immune aggregate infusion was not desensitized by prior infusion of AGEPC. Co-infusion of the cyclooxygenase inhibitor indomethacin prevented the immune aggregate-induced glycogenolytic response but had no effect on AGEPC-stimulated hepatic glucose output. It is suggested that the mechanism by which aggregated IgG activates hepatic glycogenolysis requires the synthesis of AGEPC by the liver by a pathway which involves the metabolism of arachadonic acid.

Animals↗
PubMed1984

Rabbit platelet calcium ATPase differs from the human erythrocyte (Ca2+ + Mg2+)-ATPase in its response to three purified phospholipases A2, exogenous phospholipids and calmodulin.

Human erythrocyte (Ca2+ + Mg2+)-ATPase and calcium ATPase of rabbit platelets were compared by their responses to a variety of treatments. These included three purified phospholipases A2 (acidic, neutral and basic) from Agkistrodon halys blomhoffii, as well as several phospholipids and lysophospholipids. The erythrocyte enzyme was stimulated 2-3-fold by all three phospholipases with maximal stimulation occurring at different concentrations of the three enzymes. The basic phospholipase was the most potent, followed by the neutral and acidic enzymes in that order. The calcium ATPase activity of the platelet was also stimulated by phospholipase treatment, but only by 10-20%. The stimulatory activity was attributable to hydrolysis of a very small portion of the total membrane phospholipid. Inactivation of the phospholipases by heating or chemical modification with p-bromophenacyl bromide abolished their ability to stimulate. Addition of polyphosphoinositides stimulated both ATPases. However, another acidic phospholipid, lysophosphatidic acid, stimulated only the erythrocyte enzyme and failed to affect the platelet calcium ATPase. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) had no effect on either enzyme, while the platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine), its lyso compound and lysoPC inhibited both ATPases. Calmodulin stimulated the erythrocyte enzyme, but did not affect the platelet calcium ATPase. These results demonstrate that the protein-lipid interactions operative in the erythrocyte and platelet calcium ATPases are quite different.

Adenosine Triphosphatases↗
PubMed1984

Acetylglyceryl ether phosphorylcholine (AGEPC; platelet-activating factor)-induced stimulation of rabbit platelets: correlation between phosphatidic acid level, 45Ca2+ uptake, and [3H]serotonin secretion.

When 32Pi-labeled rabbit platelets were incubated with 5 X 10(-10) M 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC), either in the presence or absence (0.1 mM EGTA) of added Ca2+, there was a three- to five-fold increase in the [32P]phosphatidic acid (PA) pool within 15 to 20 s. This event was followed by a gradual decrease in the [32P]PA level to near basal level in 5 min. AGEPC effected this change in [32P]PA in a characteristic dose- and time-dependent manner. Polar head group analogs of AGEPC, such as AGEDME and AGEMME, also effected an increase in PA labeling at levels comparable to those previously reported for their activity toward rabbit platelets [K. Satouchi, R. N. Pinckard, L. M., McManus, and D. J. Hanahan (1981) J. Biol. Chem. 256, 4425-4432]. Other analogs, i.e., lysoGEPC and the enantiomer, sn-1-AGEPC, which are inactive toward rabbit platelets, also showed no effect on the level of [32P]PA. The finding that the PA level in rabbit platelets could be manipulated by the addition of AGEPC, without any added Ca2+, provided an excellent model system for establishing a correlation between the uptake of Ca2+, serotonin release, and PA level. Thus, PA must be regarded as a sensitive indicator of a reaction mechanism important to the platelet response to AGEPC, and could be the focal point in promoting calcium uptake during the stimulation process.

Animals↗
PubMed1984

The effect of acetylglyceryl ether phosphorylcholine on glycogenolysis and phosphatidylinositol 4,5-bisphosphate metabolism in rat hepatocytes.

The effect of acetylglyceryl ether phosphorylcholine (AGEPC) on glycogenolysis and phosphatidylinositol 4,5-bisphosphate has been studied in rat hepatocytes. Previously, this laboratory demonstrated that AGEPC stimulated glucose output from the perfused rat liver and promoted the breakdown of phosphoinositides in rat hepatocytes (Shukla, S. D., Buxton, D. B., Olson, M.S., and Hanahan, D.J. (1983) J. Biol. Chem. 258, 10212-10214). In the present study, addition of AGEPC (10(-13) to 10(-9) M) to rat hepatocytes failed to stimulate glucose output, whereas epinephrine (10(-5)M) and glucagon (10(-7)M) stimulated glucose output by 100% or more in these same cells. The effects of AGEPC, epinephrine, vasopressin, and glucagon on glycogen phosphorylase activity and the breakdown of phosphatidylinositol 4,5-bisphosphate were compared in hepatocytes. AGEPC (10(-9)M) promoted the breakdown of phosphatidylinositol 4,5-bisphosphate in a fashion similar to epinephrine (10(-5)M) and vasopressin (10(-7)M). In contrast to the two calcium-mobilizing hormones, epinephrine and vasopressin, AGEPC did not cause an activation of glycogen phosphorylase. Glucagon activation of glycogen phosphorylase was not accompanied by a significant effect on phosphatidylinositol 4,5-bisphosphate hydrolysis. Thus, AGEPC is a chemical mediator which induces the degradation of phosphatidylinositol 4,5-bisphosphate without activating glycogenolysis in hepatocytes.

Animals↗
PubMed1984

Stimulation of hepatic glycogenolysis by acetylglyceryl ether phosphorylcholine.

1-O-Alkyl-2-acetyl-sn-glyceryl 3-phosphorylcholine or acetylglyceryl ether phosphorylcholine (AGEPC) stimulated glycogenolysis in perfused livers from fed rats at concentrations as low as 10(-11) M. At the lower AGEPC concentrations, e.g. 2 X 10(-10) M, a single transient phase of enhanced hepatic glucose output was elicited upon infusion of this agonist. At higher concentrations, e.g. 2 X 10(-8) M, a sharp transient spike of glucose output was observed, followed by a stable elevated steady state rate of glucose output until the AGEPC infusion was terminated. Increased rates of lactate and acetoacetate output and a diminished hepatic oxygen consumption were characteristic of the response of the livers to AGEPC at 2 X 10(-10) M. Neither alpha- nor beta-adrenergic antagonists blocked the glycogenolytic response of AGEPC. Repeated infusion of AGEPC led to homologous desensitization of the response, but the response of the liver to the alpha-adrenergic agonist, phenylephrine, or to glucagon, subsequent to AGEPC stimulation, was unaffected. Increasing the period of perfusion between successive additions of AGEPC, from 7 to 30 min, resulted in an increased glycogenolytic response to this agonist. When the perfusate calcium concentration was reduced from 1.25 to 0.05 mM, the glycogenolytic response to AGEPC was markedly diminished; calcium efflux from the liver following stimulation with AGEPC was not observed. The data presented in this study illustrate a potent agonist effect of AGEPC on the glycogenolytic system in the rat liver.

Animals↗
PubMed1984

Metabolism of 1-O-alkyl-2-acetyl-sn-glycerol by washed rabbit platelets: formation of platelet activating factor.

A new type of neutral lipid, 1-O-alkyl-2-acetyl-sn-glycerol (AAG), induced a delayed aggregation pattern on interaction with washed rabbit platelets. Although far less potent on a molar basis than platelet activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, AGEPC, nevertheless this compound caused an aggregation, albeit delayed in time, remarkably similar to that exhibited by AGEPC. In view of the possible formation of AGEPC in this reaction, AAG was incubated with washed rabbit platelets, and a lipid corresponding in chromatographic behavior to AGEPC was isolated and identified as such by a combined gas-liquid chromatography/mass spectrometry technique coupled with selected ion monitoring.

Animals↗
PubMed1984

Modulation of platelet-activating factor (PAF) synthesis and release from human polymorphonuclear leukocytes (PMN): role of extracellular Ca2+.

Extracellular Ca2+ regulated the synthesis and release of platelet-activating factor (PAF) from human polymorphonuclear leukocytes (PMN) stimulated with N'-formyl-methionyl-leucyl-phenylalanine (FMLP) in the presence of cytochalasin B. Maximum PAF synthesis and release required the presence of 0.14 mM Ca2+ whereas 1.4 mM Ca2+ was necessary for maximum lysosomal enzyme secretion. The synthesis of PAF occurred within 2.5 min after PMN stimulation in the presence of 1.4 mM Ca2+; however, PAF release did not occur until 5 min after stimulation. Peak PAF release occurred by 7.5 min but accounted for only 30-40% of the total amount of PAF synthesized, the remainder being retained on or within the PMN. Stimulation of PMN in the presence of 0.01 M EDTA or EGTA decreased PAF synthesis and release by greater than 95%. In the absence of extracellular Ca2+, stimulated PMN synthesized PAF in amounts that were 10-30% of maximum, but there was no release of the newly synthesized PAF. At Ca2+ concentrations greater than 0.01 mM, there was a dose-dependent (up to 0.14 mM) increase in PAF synthesis that was associated with the initiation and concomitant increase in the amount of PAF released. These data suggest the presence of a PAF synthesis-release coupling mechanism in which the extracellular Ca2+-dependent release of PAF stimulates additional PAF synthesis.

Adult↗
PubMed1984

Observations on the critical micellar concentration of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine and a series of its homologs and analogs.

In a study designed to explore the physical chemical characteristics of platelet activating factor (PAF), or 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, the critical micellar concentration of this compound, as well as the propionyl, butyryl and hexanoyl homologs was determined. In addition, an analogous series of compounds, in which the 1-O-alkyl was replaced by a 1-O-hexadecanoyl or a 1-O-octadecanoyl group, were examined for their critical micellar concentration. A variety of analytical techniques including NMR, gas liquid chromatography, infra-red spectrometry, thin layer chromatography, phosphorus, choline, glyceryl ether and fatty acid analyses were used to confirm the high purity of the individual derivatives. A dye binding assay and a surface tension technique were compared as to their suitability for determination of the critical micellar concentration of these compounds. Whereas the dye binding method proved highly variable, the surface tension procedure proved to be a facile, reproducible technique and was the assay of choice. The critical micellar concentration of the 1-O-alkyl and the 1-O-acyl derivatives showed comparable values for each short chain substituent at carbon 2, with values, in microM, ranging from 1.3 +/- 0.03 for 1-O-hexadecanoyl-2-acetyl-sn-glycero-3-phosphocholine and 1.1 +/- 0.10 for 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine to 0.22 +/- 0.01 for 1-O-hexadecanoyl-2-hexanoyl-sn-glycero-3-phosphocholine and 0.18 +/- 0.03 for 1-O-hexadecyl-2-hexanoyl-sn-glycero-3-phosphocholine. The data show that at the molar concentration usually employed in biological studies with these compounds, i.e., 1 X 10(-7) to 10(-11) M, one can assume that they will be present as monomolecular species. Thus, it seems unlikely that the widely diverse biological activities of these compounds can be explained by this physical parameter.

Acylation↗
PubMed1984

Acetyl glyceryl ether phosphorylcholine (AGEPC). A putative mediator of cardiac anaphylaxis in the guinea pig.

Platelet-activating factor is a novel phospholipid that has been implicated as an important mediator of acute allergic reactions. The intravenous administration of acetyl glyceryl ether phosphorylcholine, a pure, synthetic platelet-activating factor, causes electrocardiographic changes in the rabbit similar to those which are characteristic manifestations of systemic anaphylaxis. To determine whether platelet-activating factor contributes to anaphylactic cardiac dysfunction, we measured platelet-activating factor release from the sensitized guinea pig heart challenged in vitro with specific antigen and compared the resulting cardiac dysfunction with that induced by the injection of acetyl glyceryl ether phosphorylcholine into nonsensitized hearts. The results of these studies document that, during anaphylaxis in the isolated guinea pig heart, a platelet-activating factor is released into the coronary effluent that has physicochemical and functional properties similar to those of acetyl glyceryl ether phosphorylcholine. The intracardiac administration of acetyl glyceryl ether phosphorylcholine (10(-14) to 3 X 10(-9) mol) induced dose-related decreases in left ventricular contractile force (-5 to -85%) and coronary flow (-5 to -85%), as well as impaired atrioventricular conduction. The negative inotropic effect of acetyl glyceryl ether phosphorylcholine also was present in hearts perfused at constant flow. Although, in these hearts, acetyl glyceryl ether phosphorylcholine increased coronary resistance, which may have caused regional shunting and ischemia, it is unlikely that the negative inotropic effect of acetyl glyceryl ether phosphorylcholine was secondary to changes in coronary flow, since acetyl glyceryl ether phosphorylcholine also caused a dose-dependent negative inotropic effect in the electrically paced, noncoronary-perfused left atrium and right ventricular papillary muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaphylaxis↗
PubMed1984

Morphologic basis of increased vascular permeability induced by acetyl glyceryl ether phosphorylcholine.

The potent vasoactive and leukotactic properties of acetyl glyceryl ether phosphorylcholine (AGEPC) were further characterized histologically. After intravenous infusion of colloidal carbon and local injection of AGEPC, microscopic examination of rat cremaster muscle and skin revealed histamine-like vascular labeling restricted to postcapillary venules. Ultrastructural studies demonstrated subendothelial carbon accumulation in labeled venules. In rat skin, vascular labeling with colloidal carbon was an equally sensitive indicator of AGEPC-induced vasoactivity as was Evans blue dye extravasation for the assessment of AGEPC-induced increased vascular permeability (i.e., 1 pmole of AGEPC consistently initiated both vascular labeling and increased vascular permeability). In addition to its potent vasoactive effects in rabbits and rats, concomitant leukocyte emigration was observed in venules within 15 minutes after intradermal injection of AGEPC. In rabbit skin, AGEPC was equally as potent for the induction of leukocyte infiltrates as for the stimulation of increased vascular permeability. However, the vasoactive properties of AGEPC appeared to be neutrophil independent as well as independent of mast cell and platelet stimulation; these data suggest that AGEPC may act upon the microvasculature by direct stimulation of the venular endothelial cells. Thus, the putative role of AGEPC as a potent inflammatory mediator includes both the vasoactive and the leukotactic aspects of the acute inflammatory process.

Animals↗
PubMed1984

A facile route to semi-synthesis of acetyl glycerylether phosphoethanolamine and its choline analogue.

A facile route to the semi-synthesis of acetyl glycerylether phosphoethanolamine and, subsequently, its choline analogue (platelet-activating factor) has been developed. In essence, this technique takes advantage of the fact that the phosphatidylethanolamine fraction of bovine erythrocytes contains 75-80% of a 1-O-alkyl-2 fatty acyl derivative. Isolation of the latter by silicic acid chromatography followed by base-catalyzed methanolysis allowed good recovery (60-70%) of the 1-O-alkyl-(lyso)-sn-glyceryl-3-phosphoethanolamine, which contained a mixture of long chain alkyl ethers. This compound was treated with acetic anhydride in the presence of trace amounts of perchloric acid for 45 sec to give, in excellent yield, 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphoethanolamine (AGEPE). This procedure gave a 70% yield of purified AGEPE, based on the starting component, 1-O-alkyl-(lyso)-sn-glyceryl-3-phosphoethanolamine. Separation of AGEPE into fractions individually enriched in the 16:0, 18:0, and 18:1 alkylether substituents was accomplished by silica gel G combined with silver nitrate-impregnated silica gel H thin-layer chromatography. The AGEPE or its individual molecular species can be converted in high yields to the corresponding 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphocholine (AGEPC) analogues by reaction with methyl iodide in the presence of a crown ether. Characterization of the derivatives was achieved through thin-layer chromatography, infrared spectroscopy, gas-liquid chromatography, and combined gas-liquid chromatography-mass spectrometry. The ability of these analogues to induce irreversible aggregation and secretion of serotonin from washed rabbit platelets was evaluated.

Acetylation↗