scholarly journals Effect of membrane cholesterol on phospholipid metabolism in thrombin-stimulated platelets. Enhanced activation of platelet phospholipase(s) for liberation of arachidonic acid.

1982 ◽  
Vol 257 (12) ◽  
pp. 6844-6849 ◽  
Author(s):  
R M Kramer ◽  
J A Jakubowski ◽  
R Vaillancourt ◽  
D Deykin
Keyword(s):  
Arachidonic Acid ◽  
Phospholipid Metabolism ◽  
Membrane Cholesterol

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.

scholarly journals Adrenaline Stimulation of Phospholipid Metabolism in Adipocyte Ghosts

1987 ◽  
Vol 40 (4) ◽  
pp. 405
Author(s):  
David Mann ◽  
Audrey M Bersten
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Linoleic Acid ◽  
Adenylate Cyclase ◽  
Phospholipid Metabolism ◽  
Dependent Manner ◽  
Long Chain Fatty Acids ◽  
Membrane Phospholipids ◽  
Dose Dependent ◽  
Stimulation Of

The incorporation of long-chain fatty acids into phospholipids has been detected in adipocyte ghosts that were incubated with [1_14 C] stearic, [1_14 C] linoleic or [l_14C] arachidonic acid. Adrenaline and adenosine activated this incorporation within 15 s of exposure of the ghosts to the hormones and the response was dose dependent. Maximum incorporation of labelled linoleic acid occurred at 10-5 M adrenaline and 10-7 M adenosine. The a-agonist phenylephrine and the ~-agonist isoproterenol were also shown to stimulate the incorporation of fatty acid in a dose dependent manner. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol were each labelled preferentially with linoleic or arachidonic acid. p-Bromophenacylbromide, quinacrine and centrophenoxine inhibited the adrenaline-stimulated incorporation of fatty acids into ghost membrane phospholipids, and p-bromophenacylbromide also reduced the activation of adenylate cyclase by adrenaline. NaF, an activator of adenylate cyclase, like adrenaline, stimulated the incorporation of linoleic acid into ghost membrane phospholipids.

Selective turnover of sarcolemmal phospholipids with lethal cardiac myocyte injury

1990 ◽  
Vol 259 (2) ◽  
pp. C325-C331 ◽  
Author(s):  
Y. Miyazaki ◽  
R. W. Gross ◽  
B. E. Sobel ◽  
J. E. Saffitz
Keyword(s):  
Arachidonic Acid ◽  
Cardiac Myocytes ◽  
Cardiac Myocyte ◽  
Cell Injury ◽  
Specific Radioactivity ◽  
Ischemic Injury ◽  
Phospholipid Metabolism ◽  
Neonatal Rat ◽  
Electron Microscopic ◽  
Electron Microscopic Autoradiography

To delineate the biochemical mechanisms responsible for the transition from reversible to irreversible ischemic injury, we used quantitative electron microscopic autoradiography. Specific alterations of phospholipid catabolism in individual subcellular organelles of cardiac myocytes associated with simulated ischemic injury were identified. Neonatal rat cardiac myocytes were incubated with 5 nM [3H]arachidonic acid to label loci of phospholipid turnover and were exposed to 30 microM iodoacetate to produce reversible and irreversible injury. Although only minute amounts of arachidonic acid were incorporated into sarcolemmal phospholipids under control conditions, 20- and 96-fold increases were observed under conditions leading to reversible and irreversible cell injury, respectively. Increases of 5- and 28-fold in the specific radioactivity of sarcolemmal phospholipids in reversibly and irreversibly injured cells occurred in the absence of significant alterations in the specific radioactivity of other subcellular compartments, demonstrating that accelerated phospholipid catabolism was confined essentially to the sarcolemma. Selective catabolism of sarcolemmal phospholipids, known to be highly enriched in arachidonic acid, is likely to augment local accumulation of arachidonic acid, identified recently as a second messenger regulating myocardial K+ channels. Because the biochemical integrity of the sarcolemma is critical to both electrophysiological function and viability of myocytes, the observed selective alterations of sarcolemmal phospholipid metabolism appear to be pivotal determinants of lethal myocardial injury.

scholarly journals Prostaglandin in the ventromedial hypothalamus regulates peripheral glucose metabolism

2020 ◽  
Author(s):  
Ming-Liang Lee ◽  
Hirokazu Matsunaga ◽  
Yuki Sugiura ◽  
Takahiro Hayasaka ◽  
Izumi Yamamoto ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Insulin Sensitivity ◽  
Glucose Metabolism ◽  
Unsaturated Fatty Acids ◽  
Ventromedial Hypothalamus ◽  
Phospholipid Metabolism ◽  
Biologically Active ◽  
Chow Diet ◽  
Key Enzyme ◽  
Hypothalamic Inflammation

AbstractThe hypothalamus plays a central role in monitoring and regulating systemic glucose metabolism. The brain is enriched with phospholipids containing poly-unsaturated fatty acids, which are biologically active in physiological regulation. Here, we show that intraperitoneal glucose injection induced changes in hypothalamic distribution and amount of phospholipids, especially arachidonic-acid-containing phospholipids, that were then metabolized to produce prostaglandins. Knockdown of cytosolic phospholipase A2 (cPLA2), a key enzyme for generating arachidonic acid from phospholipids, in the hypothalamic ventromedial nucleus (VMH), lowered insulin sensitivity in muscles during regular chow diet (RCD) feeding. Conversely, the down-regulation of glucose metabolism by high fat diet (HFD) feeding was improved by knockdown of cPLA2 in the VMH through changing hepatic insulin sensitivity and hypothalamic inflammation. Our data suggest that cPLA2-mediated hypothalamic phospholipid metabolism is critical for controlling systemic glucose metabolism during RCD, while continuous activation of the same pathway to produce prostaglandins during HFD deteriorates glucose metabolism.

scholarly journals Phospholipid metabolism in human neutrophils activated by N-formyl-methionyl-leucyl-phenylalanine. Degranulation is not required for release of arachidonic acid: studies with neutrophils and neutrophil-derived cytoplasts

1986 ◽  
Vol 236 (3) ◽  
pp. 829-837 ◽  
Author(s):  
E M Wynkoop ◽  
M J Broekman ◽  
H M Korchak ◽  
A J Marcus ◽  
G Weissmann
Keyword(s):  
Arachidonic Acid ◽  
Phosphatidic Acid ◽  
Receptor Occupancy ◽  
Phospholipid Metabolism ◽  
Human Neutrophils ◽  
Phospholipid Synthesis ◽  
Rapid Changes ◽  
Intracellular Organelles

Neutrophils respond to chemoattractants by aggregating, degranulating, remodelling of phospholipids and releasing arachidonic acid. To determine whether ligand-induced remodelling of phospholipids depends on redistribution of intracellular organelles (degranulation), we compared phospholipid remodelling of human neutrophils with that of neutrophil-derived cytoplasts. Cytoplasts, organelle-depleted vesicles of cytosol surrounded by plasmalemma, cannot degranulate. Without a stimulus, [3H]arachidonate was incorporated preferentially into phosphatidylinositol (PI) and phosphatidylcholine (PC). Exposure of cytoplasts and neutrophils prelabelled with [3H]arachidonate or [14C]glycerol to fMet-Leu-Phe (10(-7) M) induced rapid changes in distribution of label and mass of individual phospholipids: [3H]arachidonate in phosphatidic acid (PA) increased 500% (120 s), [14C]glycerol incorporation and mass of PA approached 200% of unstimulated values, and [3H]arachidonate in PI decreased continuously; these data are compatible with activity of a PI/PA cycle. However, the mass of PI in both preparations and [14C]glycerol label in intact neutrophils increased initially (5 s), suggesting net synthesis and mobilization of more than one pool of PI. Heterogeneity of PC pools was also observed: [3H]arachidonate was lost from PC immediately upon addition of stimulus, whereas mass and [14C]glycerol values increased. Thus, net phospholipid synthesis, redistribution of arachidonate and activation of the PI/PA cycle are immediate responses of the neutrophil to receptor occupancy by chemoattractants. Furthermore, the similarity in response to fMet-Leu-Phe of neutrophils and granule-free cytoplasts indicates that these processes are independent of degranulation.

Activation and Regulation of Platelet Phospholipases

1979 ◽  
Author(s):  
S. Rittenhouse-Simmons
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase C ◽  
Phospholipid Metabolism ◽  
Biologically Active ◽  
Phospholipase A ◽  
Oxidative Enzymes ◽  
Phospholipid Hydrolysis ◽  
Activated Platelets ◽  
Intracellular Ca ◽  
Secretory Tissue

The stimulated human platelet exhibits a number of rapid alterations in phospholipid metabolism which appear to have a significant role in promoting the thrombotic and hemostal, activity of the cell. Some of the earliest changes involve two types of phospholipid hydrolysis, resulting from the activation of at least two enzymes: 1)phospholipase(s) A, which frees arachidonic acid and 2)phosphatidylinositol (PI)-specific phospholipase C, which yields diglyceride. The action of phospholipase A and the factors which regulate it are of essential interest because this enzymatic activity governs the availahility of arachidonic acid to oxidative enzymes which, in turn, produce biologically active endoperoxides, thromboxane A2, and chemotactic hydroxy-derivatives. The activation of phospholipase A is promoted by elevated levels of intracellular Ca+2, is inhibited completely by cAMP, and is inhibited partially by indomethacin or aspirin. The nroductIon of diglyceride in response to thrombin is also blocked by cAMP. Since the enzyme is dependent upon Ca+2, it is possible that the mobilization of platelet Ca+2 stores mav be the activating event for this enzyme (phospholipase C). The rapidly (within 5 sec of stimulus)- Renerated diglvceride may then promote a membrane de-stabilization and thereby facilitate secretion. The observation of the rapid turnover of PI in activated platelets is consistent with earlier findings for stimulated secretory tissue, such as thyroid gland.

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