The increases in plasma levels of prostaglandins E2 (PGE2) and F2α at an early stage of laminitis are consistent with systemic inflammatory events and alterations in laminar microvascular function.
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 F2α may play in the development of laminitis induced by black walnut heartwood extract (BWHE).
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 F2α. Laminar tissue was collected for the isolation of laminar vessels, and responses of these vessels to PGE2 and F2α 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.
Results
Plasma levels of PGE2 and F2α 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. PGF2α was a potent contractile agonist for laminar veins, whereas laminar arteries were unresponsive.
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. PGF2α selectively constricted laminar veins, and may play a role in the vascular dysfunction that characterizes acute laminitis.
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.
Conclusion
Specific prostanoids, such as PGE2 and F2α, may be viable targets for the development of more effective therapeutic regimens for the treatment of equine laminitis.
Department of Large Animal Clinical Sciences (Noschka), Virginia Maryland Regional College of Veterinary Medicine Duck Pond Drive, Blacksburg, VA, 24071, Department of Physiology and Pharmacology, Institute of Comparative Medicine (Robertson, Moore, T Lewis, Peroni), and Department of Large Animal Medicine (Robertson, Moore, Peroni), College of Veterinary Medicine, University of Georgia, Athens, GA 30602-7389, and Department of Pediatrics (S Lewis) University of Virginia, College of Medicine, Charlottesville, VA 22908
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