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  • Author or Editor: Jan Åke Lindgren x
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Objective—To evaluate leukotriene (LT) biosynthetic capacity in lung tissue from healthy horses and horses with recurrent airway obstruction (RAO).

Sample Population—Lung parenchyma and airway specimens from 8 RAO-affected and 5 healthy horses.

Procedure—Horses were stabled for ≥ 72 hours. Blood was drawn before euthanasia, after which lung specimens were collected. Tissue strips from small airways and parenchyma were incubated in organ baths with the precursor LTA4 or stimulated with calcium ionophore A23187 or the tripeptide N-formyl- Met-Leu-Phe (fMLP), with or without exogenous arachidonic acid, in the presence of isolated blood neutrophils.

Results—Stabling induced typical clinical signs of airway obstruction in RAO-affected horses but not control horses. When lung parenchyma or airway specimens from both groups of horses were incubated with calcium ionophore, with or without arachidonic acid, they did not form LT. In contrast, addition of LTA4 to both tissues resulted in conversion to LTB4, although concentrations of LTC4 were negligible in airways and parenchymal strips from healthy and RAOaffected horses. Incubation of airway and parenchymal strips with suspensions of autologous neutrophils did not influence formation of LT stimulated by calcium ionophore or fMLP, with or without exogenous arachidonic acid.

Conclusion and Clinical Relevance—Results suggest that lung parenchyma and airway tissues themselves are not of substantial importance for LT formation in the lungs, although these tissues possessed some LTA4 hydrolase activity, enabling LTB4 formation. It may be speculated that LTB4 originates primarily from neutrophils and may play a role in the inflammatory events of RAO. (Am J Vet Res 2002; 63:794–798)

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in American Journal of Veterinary Research


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 (RAO).

Animals—6 RAO-affected and 6 control horses.

Procedure—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 (ΔPplmax); 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 106 cells.

Results—Clinical and mucus scores and ΔPplmax increased during stabling in RAO-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. ( Am J Vet Res 2004;65:289–295)

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in American Journal of Veterinary Research