Assessment of leukotriene B4 production in leukocytes from horses with recurrent airway obstruction

Objective-To determine the ex vivo leukotriene (LT) biosynthesis in peripheral blood neutrophils (PBNs) and inflammatory cells in bronchoalveolar lavage fluid (BALF) obtained from horses affected with recurrent airway obstruction (IRAO). Animals-6 RAO-affected and 6 control horses. Procedures-Before and 6, 24, and 48 hours after stabling, disease severity was determined subjectively by clinical and mucus scores and measurement of the maximal change in pleural pressure (DeltaPpl(max)); PBNs were isolated and BALF samples were examined cytologically. The PBN and BALF cells were activated with a calcium ionophore in the presence of arachidonic acid, and production of LTC4 and LTB4 was measured per 10(6) cells. Results-Clinical and mucus scores and DeltaPpl(max) increased during stabling in BAO-affected horses, but not in control horses. In neutrophils and BALF cells from both groups, production of LTB4 exceeded that of LTC4. At all times, LTB4 production by PBNs was less in RAO-affected horses than it was in control horses. Before stabling, LTB4 production by cells in BALF was low in RAO-affected horses, but increased considerably after 6 hours of stabling. This increase coincided with the migration of neutrophils into the airways. In control horses, production of LTB4 did not change during stabling. Conclusions and Clinical Relevance-Results suggested increased production of LTB4 in airways of RAO-affected horses, compared with control horses, that may contribute to the infiltration of neutrophils into the lungs and the sustained inflammation associated with RAO.