Mediators of Passive Lung Anaphylaxis in the Rat

Passive lung anaphylaxis (PLA) was investigated in rats sensitized by the intravenous injection of high titre reaginic antiserum prepared in rats. 2 The effect of various pharmacological antagonists on anaphylactic bronchoconstriction in vivo were examined. An antihistamine (mepyramine), a kallikrein inactivator (aprotinin) or a prostaglandin synthesis inhibitor (aspirin) did not inhibit PLA, whereas an anti-5-hydroxytryptamine agent (methysergide) and an anti-slow reacting substance-A agent (FPL 55712) significantly reduced the response. 3 Isolated perfused lungs taken from sensitized rats released, on challenge with the sensitizing antigen, histamine, 5-hydroxytryptamine, slow reacting substance of anaphylaxis (SRS-A) and prostaglandins, but no rabbit aorta contracting substance (RCS). 4 Disodium cromoglycate inhibited both anaphylactic bronchoconstriction in vivo and the anaphylactic release of mediators in vitro. Inhibition in vivo was dose-related. 5 Mediators from the intestine, the primary shock organ of anaphylaxis in the rat, did not contribute to the lung response. 6 Vagal reflex pathways were found not to be important in PLA in vivo. 7 The relationship between the mediators released following antigen challenge of passively sensitized rat lung in vitro and passive lung anaphylaxis in vivo is discussed.