Characterization of arachidonic acid metabolism, superoxide production, and bacterial killing by bovine alveolar neutrophils elicited with leukotriene B₄ and zymo-san-activated plasma

Abstract

Leukotriene B₄ (LTB₄) and zymosan-activated plasma (ZAP) were each instilled into the lungs of steers to elicit alveolar neutrophils for subsequent functional analysis. Prior to instillation of either agent, bronchoalveolar lavage cell populations consisted of 95.8 ± 0.4% macrophages (mean ±SEM). Four hours after instillation of LTB₄ or ZAP, the lavage cell populations consisted of 75.0 ± 8.8% and 90.7 ± 0.7% neutrophils, respectively. Alveolar neutrophils elicited with LTB₄ and stimulated with the calcium ionophore A23187 released diminished amounts of LTB₄ and increased amounts of 5-hydroxyeicosatetraenoic acid (5-HETE) as compared to circulating neutrophils. Release of superoxide anion was decreased for LTB₄-elicited alveolar neutrophils as compared to circulating cells, while bacterial killing was unchanged. ZAP-elicited alveolar neutrophils released diminished amounts of LTB₄ when stimulated with A23187 as compared to circulating neutrophils. There were no differences observed in 5-HETE levels between the two cell populations. In addition, release of superoxide anion was diminished among ZAP-elicited alveolar cells, while bacterial killing was unchanged. Incubation of circulating neutrophils with LTB₄ did not influence the release of arachidonate metabolites, superoxide anion, or bacterial killing. However, incubation of circulating neutrophils with ZAP, followed by A23187 resulted in a reduction in the release of LTB₄, as compared to control cells. Prior exposure to ZAP did not influence the release of superoxide anion or bacterial killing by the circulating neutrophils.