An investigation of the involvement of platelet activating factor in the non-histamine immediate hypersensitivity reaction in the rat peritoneal cavity.

Synthetic PAF-acether injected intraperitoneally (i.p.) into sham-sensitized rats, caused dose-dependent extravasation of plasma proteins into the peritoneal fluids. Platelet aggregating activity was detected in the peritoneal fluids. In rats that had been passively sensitized for a non-histamine mediated immediate hypersensitivity reaction, antigen challenge caused extravasation of plasma proteins into the peritoneal fluids. No platelet aggregating activity was detected in these fluids. PAF is unlikely to be the mediator of extravasation in the non-histamine mediated immediate hypersensitivity reaction in the rat.