Potentiation of arachidonic acid release by phorbol myristate acetate in platelets is not due to inhibition of arachidonic acid uptake or incorporation into phospholipids. 1991

H S Banga, and S P Halenda, and M B Feinstein
Department of Pharmacology, University of Connecticut Health Center, Farmington 06032.

Activators of protein kinase C, such as tumor-promoting phorbol esters (e.g., phorbol myristate acetate), mezerein, (-)-indolactam V and 1-oleoyl 2-acetoyl glycerol, potentiate arachidonic acid release caused by elevation of intracellular Ca2+ with ionophores. This action of protein kinase C-activators required protein phosphorylation, and was attributed to enhanced hydrolysis of phospholipids by phospholipase A2 (Halenda, et al. (1989) Biochemistry 28, 7356-7363). Recently Fuse et al. ((1989) J. Biol. Chem 264, 3890-3895) reported that the apparent enhanced release of arachidonate was actually due to inhibition of the processes of re-uptake and re-esterification of released arachidonic acid. They attributed this to loss of arachidonyl-CoA synthetase and arachidonyl-CoA lysophosphatide acyltransferase activities, which were measured in membranes obtained from phorbol myristate acetate-treated platelets. In this paper, we show that phorbol myristate acetate, at concentrations that strongly potentiate arachidonic acid release, does not inhibit either arachidonic acid uptake into platelets or its incorporation into specific phospholipids. Furthermore, the fatty acid 8,11,14-eicosatrienoic acid, a competitive substrate for arachidonyl-CoA synthetase, totally blocks arachidonic acid uptake into platelets, but, unlike phorbol myristate acetate, does not potentiate arachidonic acid release by Ca2+ ionophores. We conclude that the action of phorbol myristate acetate is to promote the process of arachidonic acid release by phospholipase A2.

UI MeSH Term Description Entries
D010743 Phospholipids Lipids containing one or more phosphate groups, particularly those derived from either glycerol (phosphoglycerides see GLYCEROPHOSPHOLIPIDS) or sphingosine (SPHINGOLIPIDS). They are polar lipids that are of great importance for the structure and function of cell membranes and are the most abundant of membrane lipids, although not stored in large amounts in the system. Phosphatides,Phospholipid
D001792 Blood Platelets Non-nucleated disk-shaped cells formed in the megakaryocyte and found in the blood of all mammals. They are mainly involved in blood coagulation. Platelets,Thrombocytes,Blood Platelet,Platelet,Platelet, Blood,Platelets, Blood,Thrombocyte
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000001 Calcimycin An ionophorous, polyether antibiotic from Streptomyces chartreusensis. It binds and transports CALCIUM and other divalent cations across membranes and uncouples oxidative phosphorylation while inhibiting ATPase of rat liver mitochondria. The substance is used mostly as a biochemical tool to study the role of divalent cations in various biological systems. 4-Benzoxazolecarboxylic acid, 5-(methylamino)-2-((3,9,11-trimethyl-8-(1-methyl-2-oxo-2-(1H-pyrrol-2-yl)ethyl)-1,7-dioxaspiro(5.5)undec-2-yl)methyl)-, (6S-(6alpha(2S*,3S*),8beta(R*),9beta,11alpha))-,A-23187,A23187,Antibiotic A23187,A 23187,A23187, Antibiotic
D001095 Arachidonic Acids Eicosatetraenoic Acids,Acids, Arachidonic,Acids, Eicosatetraenoic
D013755 Tetradecanoylphorbol Acetate A phorbol ester found in CROTON OIL with very effective tumor promoting activity. It stimulates the synthesis of both DNA and RNA. Phorbol Myristate Acetate,12-Myristoyl-13-acetylphorbol,12-O-Tetradecanoyl Phorbol 13-Acetate,Tetradecanoylphorbol Acetate, 4a alpha-Isomer,12 Myristoyl 13 acetylphorbol,12 O Tetradecanoyl Phorbol 13 Acetate,13-Acetate, 12-O-Tetradecanoyl Phorbol,Acetate, Phorbol Myristate,Acetate, Tetradecanoylphorbol,Myristate Acetate, Phorbol,Phorbol 13-Acetate, 12-O-Tetradecanoyl,Tetradecanoylphorbol Acetate, 4a alpha Isomer
D015126 8,11,14-Eicosatrienoic Acid A 20-carbon-chain fatty acid, unsaturated at positions 8, 11, and 14. It differs from arachidonic acid, 5,8,11,14-eicosatetraenoic acid, only at position 5. Homo-gamma Linolenic Acid,8,11,14 Eicosatrienoic Acid,Dihomo-gamma-Linolenic Acid,Dihomogammalinolenic Acid,Ro 12-1989,Dihomo gamma Linolenic Acid,Homo gamma Linolenic Acid,Linolenic Acid, Homo-gamma,Ro 12 1989,Ro 121989
D016718 Arachidonic Acid An unsaturated, essential fatty acid. It is found in animal and human fat as well as in the liver, brain, and glandular organs, and is a constituent of animal phosphatides. It is formed by the synthesis from dietary linoleic acid and is a precursor in the biosynthesis of prostaglandins, thromboxanes, and leukotrienes. (all-Z)-5,8,11,14-Eicosatetraenoic acid,Arachidonic Acid, (all-Z)-Isomer, 1-(14)C-Labeled,Arachidonic Acid, (all-Z)-isomer, 3H-Labeled,Arachidonic Acid, Ammonium Salt, (all-Z)-Isomer,Arachidonic Acid, Cerium Salt, (all-Z)-Isomer,Arachidonic Acid, Cesium Salt, (all-Z)-Isomer,Arachidonic Acid, Lithium Salt, (all-Z)-Isomer,Arachidonic Acid, Potassium Salt, (all-Z)-Isomer,Arachidonic Acid, Sodium Salt,Arachidonic Acid, Sodium Salt, (all-Z)-Isomer,Arachidonic Acid, Zinc Salt, (all-Z)-Isomer,Sodium Arachidonate,Vitamin F,Arachidonate, Sodium
D066298 In Vitro Techniques Methods to study reactions or processes taking place in an artificial environment outside the living organism. In Vitro Test,In Vitro Testing,In Vitro Tests,In Vitro as Topic,In Vitro,In Vitro Technique,In Vitro Testings,Technique, In Vitro,Techniques, In Vitro,Test, In Vitro,Testing, In Vitro,Testings, In Vitro,Tests, In Vitro,Vitro Testing, In

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