Evaluation of the possible role of prostaglandin F₂α in laminitis induced in horses by nasogastric administration of black walnut heartwood extract | Evaluation of the possible role of prostaglandin F(2)alpha in laminitis induced in horses by nasogastric administration of black walnut heartwood extract

Obective—To provide insights into the role of prostaglandin F₂α (PGF₂α) in the developmental stages of laminitis induced in horses by ingestion of black walnut heartwood extract (BWHE). Sample Population—10 adult mixed-breed horses. Procedures—Horses were separated into 2 groups and were euthanatized at 12 hours after placebo (water) administration (control horses) or after BWHE administration and development of Obel grade 1 laminitis. Blood samples were obtained to determine plasma PGF2α concentrations hourly for the first 4 hours and subsequently every 2 hours after substance administration. Laminar arteries and veins were isolated, and responses to increasing concentrations of PGF₂α were measured before and after preincubation of blood vessels with prostanoid and thromboxane receptor antagonists SQ 29,548, SC-19220, and AH 6809. Results—Plasma PGF₂α concentrations increased in horses given BWHE; the WBC count decreased concurrently. In control horses, PGF₂α was a potent contractile agonist for laminar veins but not for laminar arteries. In horses given BWHE, PGF₂α was similarly selective for laminar veins; however, the magnitude of PGF2α-induced venoconstriction was less than that in control horses. After preincubation with SQ 29,548, laminar veins from control horses responded to PGF₂α with a small degree of dilation, whereas laminar veins from horses given BWHE did not. Conclusions and Clinical Relevance—PGF₂α may play a role in the inflammatory and vascular dysfunction associated with the prodromal stages of laminitis. Prostanoids such as PGF₂α may be viable targets for the prevention of acute laminitis in horses.

Erik Noschka, James N. Moore, John F. Peroni, Tristan H. Lewis, Stephen J. Lewis, Tom P. Robertson