Antigen-induced contraction of guinea pig isolated pulmonary arteries and lung parenchyma

We characterized the kinetics of and determined the mediators involved in antigen-induced contraction of pulmonary arteries (PA) and lung parenchyma isolated from actively sensitized guinea pigs. Ovalbumin (10^-2 mg/ml) induced contractions of PA rings, which reached maximum amplitude by 2 min and decayed to 50% of maximum by 4-6 min. Pyrilamine (10^-6 M) delayed the onset of contraction and decreased the peak of the response by >50%. Metiamide (10^-4 M) partially reversed this effect. The addition of indomethacin (10^-6 M) to the combination of pyrilamine and metiamide had no significant effect. The further addition of the leukotriene (LT) D₄/LTE₄ receptor antagonist SKF 104353 (10^-5 M) reduced the contraction by >80%. The maximum amplitude of antigen-induced contraction of parenchymal strips was reached by 15 min and was sustained for >60 min. In these tissues, SKF 104353 inhibited the contraction by ~35%, but the histamine receptor antagonists and indomethacin had no significant effect. These results suggest that both histamine and sulfidopeptide LTs mediate antigen-induced contraction of PA, whereas sulfidopeptide LTs, but not histamine, are involved in the parenchymal response.