Selective implication of thromboxane A2 and PAF-acether in two guinea pig anaphylactic models.

In an IgE and an IgG model of anaphylaxis in the guinea pig, we investigated the role of prostanoids and PAF-acether in the tracheal response in vitro to immunochallenge. Indomethacin (10(-6) M) potentiated the antigen-induced contraction in both models suggesting the synthesis of relaxant prostaglandins during the anaphylactic phenomenon. UK-38,485 (10(-5) M), a thromboxane (TxA2) synthetase inhibitor, did not modify the tracheal response in the IgE model. In the IgG model, this drug reduced the response of the tracheal strips to antigen. Ro 19-3704 (10(-6) M) and BN 52021 (10(-5) M), two potent PAF antagonists, reduced antigen-induced contraction of the tracheal strips in the IgE model. These two drugs did not modify the contractile response in the IgG model. These results indicate that PAF-acether and TxA2 play a role in the IgE and IgG model of anaphylaxis, respectively.