Mechanism of arachidonic acid liberation in platelet-activating factor-stimulated human polymorphonuclear neutrophils

Journal Article · Tue Aug 15 00:00:00 EDT 1989 · Journal of Immunology; (USA)

OSTI ID:5564528

Nakashima, S; Suganuma, A; Sato, M; Tohmatsu, T; Nozawa, Y ^[1]

---

1. Gifu Univ. School of Medicine (Japan)

Upon stimulation of human polymorphonuclear neutrophils with platelet-activating factor (PAF), arachidonic acid (AA) is released from membrane phospholipids. The mechanism for AA liberation, a key step in the synthesis of biologically active eicosanoids, was investigated. PAF was found to elicit an increase in the cytoplasmic level of free Ca2+ as monitored by fluorescent indicator fura 2. When (3H) AA-labeled neutrophils were exposed to PAF, the enhanced release of AA was observed with a concomitant decrease of radioactivity in phosphatidylinositol and phosphatidylcholine fractions. The inhibitors of phospholipase A2, mepacrine and 2-(p-amylcinnamoyl)-amino-4-chlorobenzoic acid, effectively suppressed the liberation of (3H)AA from phospholipids, indicating that liberation of AA is mainly catalyzed by the action of phospholipase A2. The extracellular Ca2+ is not required for AA release. However, intracellular Ca2+ antagonists, TMB-8 and high dose of quin 2/AM drastically reduced the liberation of AA induced by PAF, indicating that Ca2+ is an essential factor for phospholipase A2 activation. PAF raised the fluorescence of fura 2 at concentrations as low as 8 pM which reached a maximal level about 8 nM, whereas more than nM order concentrations of PAF was required for the detectable release of (3H)AA. Pretreatment of neutrophils with pertussis toxin resulted in complete abolition of AA liberation in response to PAF. However, the fura 2 response to PAF was not effectively inhibited by toxin treatment. In human neutrophil homogenate and membrane preparations, guanosine 5'-O-(thiotriphosphate) stimulated AA release and potentiated the action of PAF. Guanosine 5'-O-(thiodiphosphate) inhibited the effects of guanosine 5'-O-(thiotriphosphate).

• OSTI ID: 5564528
• Journal Information: Journal of Immunology; (USA), Vol. 143:4; ISSN 0022-1767
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ARACHIDONIC ACID
SECRETION
BLOOD COAGULATION FACTORS
BIOCHEMICAL REACTION KINETICS
LIPASE
ENZYME ACTIVITY
BIOLOGICAL PATHWAYS
CALCIUM COMPOUNDS
CELL MEMBRANES
ENZYME INHIBITORS
FRACTIONATION
MAN
NEUTROPHILS
PHOSPHOLIPIDS
RECEPTORS
TOXINS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
ANTIGENS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY FLUIDS
CARBOXYLIC ACIDS
CELL CONSTITUENTS
COAGULANTS
DRUGS
ESTERS
HEMATOLOGIC AGENTS
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
LEUKOCYTES
LIPIDS
MAMMALS
MATERIALS
MEMBRANE PROTEINS
MEMBRANES
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PRIMATES
PROTEINS
REACTION KINETICS
SEPARATION PROCESSES
TOXIC MATERIALS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques