Antagonist affinities for PAF receptors differentially depend on the degree of macrophage activation

Antagonism of platelet activating factor‐induced chemiluminescence in guinea‐pig peritoneal macrophages in differing states of activation

“…At present, we cannot rule out the possibility that in discrete groups of cells in our study the affinity of kadsurenone for Paf receptors may have been increased, but this was not detectable in the total peritoneal cell population. Different proportions of such discrete groups of cells may have accounted for the high affinity for kadsurenone observed in our previous study (Lambrecht & Parnham, 1986) as well as for our failure to confirm preliminary findings on the relation between cell activation and Paf receptor antagonist affinity (Bittner et al, 1988). The fact that BN 52021 exhibited similar mean pA2 values to kadsurenone on Paf-stimulated guinea-pig macrophages and did not show a change in affinity with increasing cell activation suggests that BN 52021 binds to a similar site on the Paf receptor to kadsurenone.…”

“…Postulating that the high affinity of kadsurenone previously observed (Lambrecht & Parnham, 1986) was related to the high degree of activation of the macrophages by the heat-killed C. parvum, we compared the calculated affinities of the various Paf antagonists for macrophage Paf receptors with the activation state (determined as the maximal chemiluminescence responses of individual cell suspensions) of the cells. A preliminary account of some of these data has been published (Bittner et al, 1988 (Lambrecht & Parnham, 1986 (Lambrecht & Parnham, 1986 …”