(/sup 3/H)52770 RP, a platelet-activating factor receptor antagonist, and tritiated platelet-activating factor label a common specific binding site in human polymorphonuclear leukocytes

Journal Article · Mon Feb 01 04:00:00 EST 1988 · J. Pharmacol. Exp. Ther.; (United States)

OSTI ID:5175935

Marquis, O; Robaut, C; Cavero, I

In human polymorphonuclear leukocytes (PMNs), the tritiated platelet activating factor ((/sup 3/H)PAF) labels in a saturable manner a single class of binding sites with a Kd of 3.5 +/- 0.5 nM (n = 7) and a maximum binding capacity (Bmax) of 206 +/- 13 fmol/2.5 X 10(6) PMNs (n = 7). 52770 RP, a nonphospholipid antagonist of PAF receptors, fully and competitively displaced the (/sup 3/H)PAF from its binding sites with a Ki of 7.0 +/- 0.7 nM (n = 4). The high potency and the low solubility in cellular membranes of this compound led us to prepare (/sup 3/H)52770 RP. This ligand was characterized by a binding which was rapid, reversible, confined to a single site, saturable, specific and stereoselective. Its Kd and Bmax were 4.2 +/- 0.3 nM and 181 +/- 11 fmol/2.5 X 10(6) PMNs, respectively. The stereoselectivity of the binding was suggested by the 600- and 1050-fold higher potency of the d-enantiomer with respect to l-52770 RP in displacing (/sup 3/H)52770 RP or (/sup 3/H)PAF, respectively. Several PAF analogs (e.g., lyso-PAF, 2-O-methyl-lyso-PAF), which are poorly active as PAF receptor agonists in functional tests, were weak displacers of (/sup 3/H)PAF and (/sup 3/H)52770 RP. Furthermore, for a series of 14 known PAF receptor agonists or antagonists belonging to different chemical families, there was an excellent correlation (r = 0.98) between their ability to displace (/sup 3/H)PAF and (/sup 3/H)52770 RP. Thus, (/sup 3/H)52770 RP and (/sup 3/H)PAF appear to interact with the same binding site on human PMNs which is proposed to be the PAF receptor mediating functional responses.

• Research Organization: Centre de Recherche de Vitry, Vitry-sur-Seine (France)
• OSTI ID: 5175935
• Journal Information: J. Pharmacol. Exp. Ther.; (United States), Journal Name: J. Pharmacol. Exp. Ther.; (United States) Vol. 244:2; ISSN JPETA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
AZINES
AZOLES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BLOOD COAGULATION FACTORS
BLOOD PLATELETS
BODY FLUIDS
CELL CONSTITUENTS
CELL MEMBRANES
COAGULANTS
DRUGS
HEMATOLOGIC AGENTS
HETEROCYCLIC COMPOUNDS
IN VITRO
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LABELLING
LEUKOCYTES
LIGANDS
MAMMALS
MAN
MATERIALS
MEMBRANE PROTEINS
MEMBRANES
NEUTROPHILS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PRIMATES
PROTEINS
PYRIDINES
REACTION KINETICS
RECEPTORS
THIAZOLES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES