Leukotriene C₄ and B₄ in bronchoalveolar lavage fluid during biphasic allergic bronchoconstriction in sheep

To study the contribution of leukotriene C₄ (LTC₄), leukotriene D₄ (LTD₄), leukotriene B₄ (LTB₄), and inflammation to the antigen-induced late bronchial response, these leukotrienes, histamine, and cell differentials were evaluated in bronchoalveolar lavage fluid (BALF). Immediate and late responses were induced by Ascaris suum antigen inhalation in 11 conscious sheep. Bronchoalveolar lavage was performed on 3 separate test days, before challenge (control), during the immediate response, and during the late response. Leukotrienes were measured by radioimmunoassay after purification by reverse-phase high-performance liquid chromatography. LTB₄ and LTC₄ were detected in control BALF, but LTD₄ was not, LTC₄ and LTB₄ were increased in the late response (p < 0.05 compared with each control). The percent neutrophils recovered by bronchoalveolar lavage was increased during the late response, and this was significantly correlated with pulmonary resistance (p < 0.01). Histamine levels in BALF were elevated during the immediate response but not during the late response. Our results suggest that histamine and LTC₄ may contribute to the contraction of bronchial smooth muscle in the immediate and the late response, respectively. The increase in LTB₄, a neutrophil chemotactic factor, during the late response may be responsible for the increase in the percent neutrophils.