Altered phospholipid metabolism in thrombin-stimulated human platelets

1984 ◽  
Vol 62 (6) ◽  
pp. 341-351 ◽  
Author(s):  
Bruce J. Holub
Keyword(s):  
Arachidonic Acid ◽  
Species Composition ◽  
Phospholipid Metabolism ◽  
Human Platelets ◽  
Inositol Triphosphate ◽  
Molecular Species Composition ◽  
The Past ◽  
Free Arachidonic Acid ◽  
The Individual ◽  
Individual Enzyme

Extensive research during the past few years has indicated that dramatic alterations in phospholipid metabolism and composition represent early and important biochemical events in the response of human platelets to thrombin stimulation. The individual enzyme-catalyzed steps which provide for the release of free arachidonic acid for thromboxane A2 formation via the initial degradation of phosphatidylcholine and phosphatidylinositol have been studied. Their importance in this regard is influenced by the molecular species composition of the corresponding phospholipid precursors. A role for stimulated phosphatidylinositol 4,5-bisphosphate degradation in the phosphatidylinositol response and inositol triphosphate release associated with calcium mobilization has also been proposed. The 1,2-diacylglycerol released by the action of phospholipase C on phosphatidylinositol and its 4,5-bisphosphate derivative has been implicated as an activator of protein phosphorylation; the derived phosphatidic acid has been proposed as a mediator for promoting an intracellular flux of calcium associated with platelet responses.

Transfer of arachidonic acid from phosphatidylcholine to phosphatidylethanolamine during storage of human platelets for 5 days

1990 ◽  
Vol 68 (1) ◽  
pp. 117-122 ◽  
Author(s):  
Julie Lacasse ◽  
Rosalind S. Labow ◽  
Morris Kates ◽  
George A. Adams
Keyword(s):  
Arachidonic Acid ◽  
Storage Conditions ◽  
Phospholipid Metabolism ◽  
Human Platelets ◽  
Acyl Transfer ◽  
Acid Uptake ◽  
Molar Composition ◽  
Platelet Storage ◽  
Head Groups ◽  
Glycerol Uptake

Human platelets are routinely stored for 5 days prior to transfusion, but they deteriorate during storage. Since very little information is available concerning the effect of storage on platelet phospholipid metabolism, the biosynthesis and remodelling of platelet phospholipids were studied. Platelets were incubated separately with [14C]glycerol, [14C]arachidonic acid, or a mixture of [14C]glycerol and [3H]arachidonic acid, and stored in a platelet storage medium at 22 °C. Maximum glycerol uptake (20%) was attained after 6 h. [14C]Glycerol was incorporated into phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol, and to a much lesser extent phosphatidylserine, under storage conditions for 5 days. The distribution of the initial arachidonic acid uptake was not as would be expected based on the molar composition of endogenous phospholipids. The arachidonic acid (75%) which was taken up within 10 min of incubation distributed 55% into the phosphatidylcholine and only 14% into the phosphatidylethanolamine; the molar composition is actually 18% phosphatidylcholine and 47% phosphatidylethanolamine. During storage, there was a continuous transfer of the radiolabeled arachidonic acid from phosphatidylcholine to phosphatidylethanolamine until, after 5 days, the distribution of arachidonic acid was identical to the endogenous distribution. In contrast, no change in the glycerol incorporation pattern was detected during storage. This suggested that the mechanism for arachidonic acid redistribution was not through exchange of polar head groups, but through acyl transfer of arachidonic acid from phosphatidylcholine to phosphatidylethanolamine.Key words: human, platelet, storage, arachidonate, phospholipids.

Molecular species of phospholipid in rats in primary and transplanted fibrosarcomas induced by soybean oil containing tocopherol acetate

1991 ◽  
Vol 69 (9) ◽  
pp. 655-660 ◽  
Author(s):  
Masataka Ishinaga ◽  
Masanori Tanimoto ◽  
Sumi Sugiyama ◽  
Rika Kumamoto ◽  
Kenjirou Yokoro
Keyword(s):  
Arachidonic Acid ◽  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Species Composition ◽  
Soybean Oil ◽  
Molecular Species ◽  
The Other ◽  
Transplanted Tumors ◽  
Molecular Species Composition ◽  
Tocopherol Acetate

When soybean oil containing tocopherol acetate was given to rats once a week subcutaneously for 10–12 months, it caused the development of fibrosarcomas at the injection site in 11 of 15 rats. A tumor produced in this manner proved eminently transplantable into other rats. The molecular species of phospholipid subclasses were determined in primary and transplanted tumors. The molecular species composition of the phospholipid subclasses in both types of tumors were similar. The percentages of diacyl and alkylacyl glycerophosphocholine (GPC) were 90–93 and 6–8% of total phosphatidylcholine, respectively. The percentages of diacyl and alkenylacyl glycerophosphoethanolamine (GPE) were 51 and 45%, respectively, of total phosphatidylethanolamine (PE). Diacyl and alkylacyl GPC species containing arachidonic acid (20:4) composed about 15–16 and 37–40% of each subclass, respectively. Diacyl and alkenylacyl GPE species containing 20:4 composed about 38–40 and 56–60% of each subclass, respectively. Disaturated species of diacyl and alkylacyl GPC composed about 22–24 and 13% of each subclass, respectively, whereas these species of PE composed less than 2%. The fatty acid composition of the other tumor phospholipids was analyzed.Key words: phospholipids, molecular species, fibrosarcomas, tocopherol, soybean oil.

The relative degradation of [14C]eicosapentaenoyl and [3H]arachidonoyl species of phosphatidylinositol and phosphatidylcholine in thrombin-stimulated human platelets

1986 ◽  
Vol 64 (12) ◽  
pp. 1256-1261 ◽  
Author(s):  
Bonnie J. Weaver ◽  
Bruce J. Holub
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Phosphatidic Acid ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
The Other ◽  
Preferential Loss ◽  
Marked Selectivity ◽  
The Individual ◽  
Layer Chromatography

The platelet-rich plasma from volunteers who had consumed a supplement containing eicosapentaenoate (EPA) was incubated with [3H]arachidonic acid (AA) and [14C]EPA so as to provide for the labelling of these fatty acids in the individual platelet phospholipids. Washed dual-labelled platelet suspensions were prepared and incubated with and without thrombin in the presence of BW755C and in the presence and absence of trifluoperazine (TFP) or indomethacin. The platelet lipids were extracted and the individual phospholipids, as well as diacylglycerol and phosphatidic acid, were separated by thin-layer chromatography and the radioactivity in each fraction was determined. The [H]AA/[14C]EPA dpm ratio for the loss of radioactivity from phosphatidylcholine (PC) upon thrombin stimulation, as well as that in the residual PC remaining after stimulation, was similar to that in PC in the resting platelets. This suggests no marked selectivity in the degradation of EPA- versus AA-containing species of PC during platelet activation. The [3H]/[14C] ratios for the increased radioactivity appearing in diacylglycerol (DG) and phosphatidic acid (PA) upon thrombin stimulation were not significantly different from the corresponding ratio in phosphatidylinositol (PI) from resting platelets, suggesting little or no preference for 1-acyl-2-eicosapentaenoyl PI over 1-acyl-2-arachidonoyl PI in the pathway from PI to DG to PA. These results suggest that the relative formation of the 2- and 3-series prostaglandins, including thromboxane (Tx) A2 and A3, in stimulated platelets is not regulated by a preferential loss of one of the corresponding eicosanoid precursors over the other from membrane PC and PI.

Binding of Recombinant Apolipoprotein(a) to Human Platelets and Effect on Platelet Aggregation

2001 ◽  
Vol 85 (04) ◽  
pp. 686-693 ◽  
Author(s):  
C. Martínez ◽  
J. Rivera ◽  
S. Loyau ◽  
J. Corral ◽  
R. González-Conejero ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Binding Sites ◽  
Human Platelets ◽  
Scatchard Analysis ◽  
High Concentration ◽  
Single Class ◽  
Apo B ◽  
Platelet Surface ◽  
The Individual

SummaryThe interaction of lipoprotein(a) [Lp(a)] with platelets is not well defined, particularly with regards to the individual contribution of the protein components of Lp(a), the apo B-100 and the apolipoprotein apo(a). This study investigated the binding of different recombinant apo(a) [r-apo(a)] isoforms, to human platelets and its effect on platelet aggregation. Scatchard analysis of saturation binding experiments demonstrated that human platelets display a single class of high affinity r-apo(a) binding sites (71 ± 46 molec./platelet, Kd = 5.6 ± 2.0 nmol/L). Platelet activation with strong agonists (thrombin, arachidonic acid) increased 2- to 10-fold the r-apo(a) binding, without affecting the affinity. Competition assays showed that the binding sites are highly specific for r-apo(a) and Lp(a). At high concentration t-PA could also bind to the r-apo(a) binding sites. By contrast, neither fibrinogen nor plasminogen inhibited to the r-apo(a) binding. The lysine analogue EACA inhibits the binding of r-apo(a) to platelets, thus suggesting the involvement of lysine residues in that interaction. Moreover, the r-apo(a) binding to platelets is unlikely mediated by GPIIb/IIIa-attached fibrin since it is not affected by platelet treatment with either LJ-CP8, a monoclonal antibody that specifically blocks fibrinogen binding to GPIIb/IIIa, nor GPRP, an inhibitor of fibrin polymerisation. Finally, we show that the distinct recombinant apo(a) proteins, as well as native Lp(a), promote an aggregation response of platelets to otherwise subaggregant doses of arachidonic acid. This proaggregant effect of r-apo(a) is dependent on its binding to platelets since it requires a minimum incubation time, and it is prevented by EACA at concentration inhibiting the r-apo(a)-platelet interaction.These results suggest that the prothrombotic action of Lp(a) may be in part mediated by modulating the platelet function through the interaction of its apo(a) subunit with a specific receptor at the platelet surface.

Effect of Dilazep on Phospholipid Metabolism and Arachidonic Acid Cascade in Human Platelets in vitro

1984 ◽  
Vol 12 (2) ◽  
pp. 363-370
Author(s):  
Mitsuko TAKENAGA ◽  
Haruo KITAGAWA ◽  
Aizan HIRAI ◽  
Yasushl TAMURA ◽  
Sho YOSHIDA
Keyword(s):  
Arachidonic Acid ◽  
Phospholipid Metabolism ◽  
Human Platelets ◽  
Arachidonic Acid Cascade

scholarly journals Phospholipid molecular species composition of mouse liver nuclei. Influence of dietary n–3 fatty acid ethyl esters

1992 ◽  
Vol 287 (1) ◽  
pp. 237-240 ◽  
Author(s):  
R S Chapkin ◽  
L D Davidson ◽  
L A Davidson
Keyword(s):  
Species Composition ◽  
Molecular Species ◽  
Mouse Liver ◽  
Ethyl Esters ◽  
Safflower Oil ◽  
Molecular Species Composition ◽  
Individual Molecular Species ◽  
Phospholipid Molecular Species ◽  
Liver Nuclei ◽  
The Individual

The effect of dietary eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) ethyl esters on the individual molecular species composition of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was determined in mouse liver nuclei. After a 10 day feeding period, there was a depletion of the sn-2 position of n-6 polyunsaturated fatty acids (PUFA) and substitution with n-3 PUFA. EPA feeding significantly increased (P less than 0.05) diacyl PC and PE 16:0-20:5, n-3, 16:0-22:6,n-3, 18:0-20:5,n-3 and 18:0-22:6,n-3 relative to control (safflower oil ethyl ester fed) animals. In comparison, DHA feeding significantly increased (P less than 0.05) 22:6 n-3-containing species, specifically 18:1-22:6,n-3, 16:0-22:6,n-3 and 18:0-22:6,n-3 in PC, and 18:1-22:6,n-3, 16:0-22:6,n-3 and 18:0-22:6,n-3 in PE. In addition, the presence of 18:0-20:5,n-3 PC in the nuclei of DHA-fed rats and of 18:2-20:5,n-3, 18:1-20:5,n-3 and 18:0-20:5,n-3 in nuclear PE indicate that incorporation of DHA retroconversion (22:6,n-3–>20:5,n-3) products. These results indicate both EPA and DHA are extensively incorporated into nuclear phospholipids, and therefore could potentially influence gene function.

scholarly journals Activation of human platelet phospholipase C by ionophore A23187 is totally dependent upon cyclo-oxygenase products and ADP

1984 ◽  
Vol 222 (1) ◽  
pp. 103-110 ◽  
Author(s):  
S E Rittenhouse
Keyword(s):  
Arachidonic Acid ◽  
Phosphatidic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Human Platelet ◽  
Human Platelets ◽  
Dense Granule ◽  
Ionophore A23187 ◽  
Free Arachidonic Acid ◽  
Stimulation Of

Human platelets exposed to the Ca2+ ionophore A23187 form cyclo-oxygenase metabolites from liberated arachidonic acid and secrete dense granule substituents such as ADP. I have shown previously that A23187 causes activation of phospholipase A2 and some stimulation of phospholipase C. I now report that, in contrast to the case for thrombin, the activation of phospholipase C in response to ionophore is completely dependent upon the formation of cyclo-oxygenase products and the presence of ADP. The addition of A23187 to human platelets induces a transient drop in the amount of phosphatidylinositol 4,5-bisphosphate, a decrease in the amount of phosphatidylinositol, and the formation of diacylglycerol and phosphatidic acid. In addition, lysophosphatidylinositol and free arachidonic acid are produced. The presence of cyclo-oxygenase inhibitors or agents which remove ADP partially impairs these changes. When both types of inhibitor are present, the changes in phosphatidylinositol 4,5-bisphosphate and the formation of diacylglycerol and phosphatidic acid are blocked entirely, whereas formation of lysophosphatidylinositol and free arachidonic acid are relatively unaffected. The prostaglandin H2 analogue U46619 activates phospholipase C. This stimulation is inhibited partially by competitors for ADP. I conclude that phospholipase C is not activated by Ca2+ in the platelet, and suggest that stimulation is totally dependent upon a receptor coupled event.

Antithrombin III Antigen in Human Platelets

1985 ◽  
Vol 54 (03) ◽  
pp. 599-602 ◽  
Author(s):  
M Léon Alhenc-Gelas ◽  
M Aiach ◽  
A Gorenflot ◽  
J P Andreux
Keyword(s):  
Arachidonic Acid ◽  
Enzyme Immunoassay ◽  
Antithrombin Iii ◽  
Human Platelets ◽  
Mean Value ◽  
Normal Blood ◽  
Freezing And Thawing ◽  
Healthy Donors ◽  
At Iii ◽  
Storage Granules

SummaryImmunoreactive AT III was found in human platelets. AT III antigen was quantified in platelets taken from each of 17 healthy donors by a specific competitive enzyme immunoassay using purified AT III and AT III antibodies. AT III antigen levels in extracts of washed platelets disrupted by freezing and thawing ranged from 32 to 140 ng per 109 platelets with a mean value of 70.3 ± 27.3. When stimulated by arachidonic acid, the platelets released AT III antigen together with immunoreactive fibrinogen. These results show that AT III is present in platelets at a level corresponding to approximately 0.01% of total antithrombin in normal blood, and suggest that platelet AT III, like fibrinogen, is contained in the storage granules.

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