ANAPHYLACTIC ACTIONS OF PLATELET-ACTIVATING FACTOR

  • 1 January 1981
    • journal article
    • research article
    • Vol. 105  (1) , 64-69
Abstract
Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) is a potent inducer of systemic anaphylactoid reactions in animals. It was similarly potent in contracting smooth muscle of guinea pig ileum and lung, and in enhancing vascular permeability when injected s.c. into these animals. This factor possesses in vitro and in vivo bioactions that resemble those of C3a [a fragment of complement component 3] and C5a [a fragment of complement component 5] anaphylatoxins. Platelet-activating factor induces a slowly developing, sustained contractile wave in ileum that is not inhibited by an antihistaminic compound, pyrilamine, whereas C3a and C5a stimulate rapid transient contraction that is abrogated by the antihistamine. Platelet-activating factor desensitized the ileum to restimulation by itself but not by C3a or C5a. C3a and C5a desensitized the ileum to themselves but not to platelet-activating factor. Platelet-activating factor possesses a distinctive set of anaphylactic actions. It stimulates a slow wave of muscle contraction and can act independently of histamine release and receptors for the C3a and C5a anaphylatoxins.