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Radioligand binding of antagonists of platelet‐activating factor to intact human platelets
Author(s) -
Ukena Dieter,
Dent Gordon,
Birke Frank W.,
Robaut Christine,
Sybrecht Gerhard W.,
Barnes Peter J.
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)80017-6
Subject(s) - platelet activating factor , radioligand , platelet , chemistry , dissociation constant , antagonist , radioligand assay , receptor , binding site , stereochemistry , biochemistry , medicine , endocrinology , biology
Two new antagonists of platelet‐activating factor (PAF), the pyrrolothiazole derivative 52770 RP and the triazolodiazepine WEB 2086, have been studied as radioligands in intact human platelets. [ 3 H]52770 RP and [ 3 H]WEB 2086 bound specifically to high‐affinity sites with dissociation constants ( K d ) of 14.8 and 6.1 nM, respectively. The maximal number of sites for [ 3 H]52770 RP binding was approx. 15‐fold higher than for [ 3 H]PAF and [ 3 H]WEB 2086. In addition, C 16 ‐PAF, lyso‐PAF, WEB 2086 and 52770 RP had K i values which were nearly identical for both [ 3 H]PAF and [ 3 H]WEB 2086, whereas only 52770 RP competed for [ 3 H]52770 RP‐binding sites. These results demonstrate that in human platelets the sites of [ 3 H]WEB 2086 binding are identical to [ 3 H]PAF‐binding sites, whereas those of [ 3 H]52770 RP are not. [ 3 H]WEB 2086 appears, therefore, to be a suitable antagonist radioligand for labelling PAF receptors.