Prostaglandins E₂ And F_2α as Inflammatory and Vasoactive Mediators in Black Walnut Heartwood Extract-Induced Equine Laminitis

Article Outline

• Take Home Message
• Introduction
• Materials and Methods
• Results
• Discussion
• Clinical Relevance
• Conclusion
• Copyright

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Take Home Message 

The increases in plasma levels of prostaglandins E₂ (PGE₂) and F_2α at an early stage of laminitis are consistent with systemic inflammatory events and alterations in laminar microvascular function.

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Introduction 

Links between the inflammatory and vascular events during the prodromal stages of laminitis have yet to be identified. The aim of this study was to provide initial insights into the role that PGE₂ and F_2α may play in the development of laminitis induced by black walnut heartwood extract (BWHE).

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Materials and Methods 

Blood samples were collected before and after administration of either water (control horses) or BWHE for white blood cell counts and plasma concentrations of PGE₂ and F_2α. Laminar tissue was collected for the isolation of laminar vessels, and responses of these vessels to PGE₂ and F_{2 α} were determined. The data were analyzed by repeated measures analysis of variance (ANOVA). Differences between individual means were identified by Student's modified t-test using the Bonferroni correction for multiple comparisons between means using the error mean square term from the ANOVA.

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Results 

Plasma levels of PGE₂ and F_2α increased transiently and coincided with the nadir in white blood cell counts in BWHE horses. PGE₂ elicited small dilator responses in laminar veins from control horses, but elicited a small constrictor response in laminar veins from BWHE horses. PGF_2α was a potent contractile agonist for laminar veins, whereas laminar arteries were unresponsive.

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Discussion 

PGE₂ elicited vascular responses in laminar vessels in control and BWHE horses may be explained by different receptor populations and alterations in laminar tissues in BWHE horses. PGF_2α selectively constricted laminar veins, and may play a role in the vascular dysfunction that characterizes acute laminitis.

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Clinical Relevance 

The use of anti-inflammatory drugs in acute laminitis is supported by the results of this study. The effects of these drugs on responses of laminar microvessels to other PGs need to be determined.

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Conclusion 

Specific prostanoids, such as PGE₂ and F_2α, may be viable targets for the development of more effective therapeutic regimens for the treatment of equine laminitis.