In vitro reactivity of digital arteries and veins to vasoconstrictive mediators in healthy horses and in horses with early laminitis.
Authors: Baxter, Laskey, Tackett, Moore, Allen
Journal: American journal of veterinary research
Summary
# Editorial Summary Researchers examined how blood vessels in the equine foot respond to vasoactive substances implicated in laminitis pathogenesis, using isolated digital arteries and veins from healthy horses and those with early (Obel grade I) laminitis induced via carbohydrate overload. In vitro tissue bath studies assessed reactivity to five vasoconstrictive mediators—angiotensin II, norepinephrine, serotonin, prostaglandin F2α, and thromboxane analogue U46619—measuring both potency (EC50 concentration) and maximal contraction strength across a wide dose range (10⁻⁸M to 10⁻⁴M). Notably, laminitic vessels demonstrated significantly heightened sensitivity and responsiveness to multiple vasoconstrictors compared with healthy controls, suggesting that endothelial dysfunction in early laminitis amplifies the foot's vascular reactivity to circulating mediators that would normally produce minimal constriction. These findings support the hypothesis that vasoconstriction contributes meaningfully to laminitis pathophysiology rather than being incidental, and indicate that therapeutic strategies targeting vascular tone or mediator release merit investigation as potential preventative or early-intervention approaches during the critical early phases of laminitis development.
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Practical Takeaways
- •Understanding the vascular reactivity changes in laminitis may help identify therapeutic targets for managing acute laminitic episodes in clinical practice
- •The lack of endotoxin effect on baseline vascular reactivity suggests laminitis pathophysiology involves mechanisms beyond simple endotoxin-mediated vasoconstriction
- •Digital artery and vein reactivity patterns are consistent between limbs, indicating laminitis is a systemic vascular problem rather than localized to specific limbs
Key Findings
- •No differences in EC50 concentrations and maximal contractions between forelimb and hind limb digital arteries and veins for angiotensin II, norepinephrine, and serotonin in healthy horses
- •Bacterial endotoxin incubation had no effect on reactivity of arteries and veins to angiotensin II, norepinephrine, and serotonin
- •In vitro reactivity of palmar digital vessels to vasoconstrictive mediators was compared between healthy horses and horses with early laminitis using carbohydrate overload model