Interference of PCA 4248, a novel PAF receptor antagonist, with antigen-induced paw edema in mice.

The interference of the novel platelet-activating factor (PAF) receptor antagonist compound PCA 4248 with paw edema induced by antigen in sensitized boosted or unboosted mice was studied. Although PAF-induced edema was of similar intensity in non-sensitized and in both groups of sensitized mice, PCA 4248 was less effective in inhibiting paw edema induced by PAF in boosted mice. Paw edema induced by antigen in unboosted mice was refractory to PCA 4248 under conditions where edema in boosted mice was inhibited. Our results demonstrate that the PCA 4248 displays an anti-PAF activity in non-sensitized mice that is reduced by the booster injection of antigen. PAF plays an important role in the anaphylactic edema in boosted but not in unboosted mice.