RT Journal Article
SR Electronic
T1 The platelet activating factor receptor antagonist, RP 59227, blocks platelet activating factor receptors mediating liberation of reactive oxygen species in guinea pig macrophages and human polymorphonuclear leukocytes.
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 567
OP 575
VO 258
IS 2
A1 A Floch
A1 L Tahraoui
A1 P Sedivy
A1 I Cavero
YR 1991
UL http://jpet.aspetjournals.org/content/258/2/567.abstract
AB In elicited (mineral oil) peritoneal guinea pig macrophages, there was a specific [3H]platelet activating factor (PAF) binding which displayed concentration dependency, saturability, high affinity (Kd = 2.2 +/- 0.2 nM, n = 15), elevated capacity (Bmax = 122,808 +/- 10,234 sites/cell, n = 15) and irreversibility. PAF(C16) and the PAF antagonists RP 59227, Ro 19-3704 and WEB 2086 prevented the binding of [3H]PAF. RP 59227 (Ki = 3.1 +/- 0.3 nM, n = 5) was about 5- and 8-fold more potent than Ro 19-3704 and WEB 2086, respectively. In competition studies, RP 59227 produced dextral and concentration-dependent shifts of the sigmoidal inhibition curve of [3H]PAF binding by PAF(C16). Macrophages exposed to PAF produced chemiluminescence signals, the magnitude of which was concentration related (pD2 = 8.40 +/- 0.03, n = 13) and which were inhibited by the oxygen radical scavengers, superoxide dismutase, catalase, deferoxamine and mannitol. RP 59227 and WEB 2086 antagonized in a noncompetitive manner (pD'2 = 7.72 +/- 0.01 and 8.15 +/- 0.05, respectively) the control PAF concentration-response curve. By contrast, Ro 19-3704 behaved as a competitive antagonist (pA2 = 8.13 +/- 0.11). The apparent noncompetitive effects of RP 59227 were not due to undisplaceable binding to PAF receptors because washing of macrophages exposed to RP 59227 allowed the recovery of PAF luminescence and PAF binding. This procedure was poorly effective to lessen the inhibitory activity of WEB 2086. In human polymorphonuclear leukocytes, the weak potency of PAF was enhanced by 10-fold (pD2 = 7.61 +/- 0.06, n = 6) when polymorphonuclear leukocytes were primed for 10 min with fMLP (5 nM).(ABSTRACT TRUNCATED AT 250 WORDS)