Black walnut extract-induced laminitis in horses is associated with heterogeneous dysfunction of the laminar microvasculature.
Authors: Peroni, Harrison, Moore, Graves, Lewis, Krunkosky, Robertson
Journal: Equine veterinary journal
Summary
# Editorial Summary Black walnut heartwood extract (BWHE) is a known laminitis trigger, though the precise vascular mechanisms underlying the disease remain incompletely understood. Peroni and colleagues investigated whether the prodromal phase involves dysfunction of laminar blood vessels by administering BWHE or control solutions to horses, then isolating laminar arteries and veins post-euthanasia to assess their contractile responses to two potent vasoconstrictors—phenylephrine and 5-hydroxytryptamine—using small vessel myography. Whilst laminar arteries responded identically in both groups, laminar veins from BWHE-treated horses demonstrated significantly blunted contractile responses, indicating selective venous dysfunction during early laminitis. This finding suggests that impaired venous contractility—rather than arterial dysfunction—may be a critical early event in laminitis pathogenesis, potentially leading to laminar congestion and downstream tissue damage. For practitioners, these results highlight the value of understanding how vasomotor dysfunction contributes to clinical signs and point towards possible future therapeutic targets aimed at restoring venous function; however, further work is needed to establish whether correcting venous dysfunction translates to clinical benefit in naturally occurring or experimentally induced laminitis.
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Practical Takeaways
- •Black walnut exposure causes measurable vascular dysfunction in the laminae, providing mechanistic evidence for black walnut-induced laminitis; avoid exposure to black walnut heartwood and shavings
- •Laminar vein dysfunction may impair blood drainage from the hoof, contributing to inflammation and pain during laminitis development; understanding this mechanism may guide future therapeutic interventions targeting venous function
- •Selective venous dysfunction without arterial involvement suggests therapeutic targets may exist to restore venous contractility and improve outcomes in laminitis cases
Key Findings
- •Black walnut heartwood extract induced selective contractile dysfunction in laminar veins but not laminar arteries
- •Responses to phenylephrine and 5-hydroxytryptamine were significantly reduced in laminar veins from BWHE-administered horses compared to controls
- •Laminar artery contractile responses to vasoconstrictors were identical between BWHE-treated and control horses
- •Prodromal laminitis is associated with heterogeneous vascular dysfunction with preferential venous involvement