A comparative study between responses of isolated bovine and equine digital arteries to vasoactive mediators

Abstract

Hemodynamic perturbations, partly resulting from abnormal vasoconstriction of digital vessels, have been implicated in the pathogenesis of bovine and equine laminitis.This study compared the responsiveness of isolated bovine (BDA) and equine (EDA) digital arteries to pharmacological agents that stimulate receptor systems involved in the regulation of normal vessel tone. The role of the endothelium and the short-and longer-term effects of an experimentally induced endothelial damage were also evaluated. Species-related differences were found in the vessel reactivity to all of the receptor agonists tested. In intact BDA, as compared to intact EDA, norepinephrine was a more effective vasoconstrictor, 5-hydroxytryptamine a more effective but less potent vasoconstrictor, isoproterenol a less effective vasodilator and carbamylcholine a less potent vasodilator. In BDA, but not in EDA, the contractile responses to norepinephrine and 5-hydroxytryptamine were enhanced immediately after endothelium removal. However, the contractile reactivity of denuded BDA returned to basal values following overnight incubation. The differences suggest species specificity for the pathophysiology of digital vasomotor tone and function in horses and cattle.

Endothelium‐dependent relaxation mechanisms involve nitric oxide and prostanoids in the isolated bovine digital vein

“…In contrast to the equine species, the basic knowledge behind the response of the bovine digital vasculature has not been extensively studied (Zizzadoro et al., ). Elmes and Eyre () reported the response of the bovine digital artery and vein to different vasoactive agents.…”

“…The participation of the Rho kinase pathway in the 5‐HT enhanced contraction after an in vitro experimental model of long‐term endothelial denudation was reported in the bovine digital vein (Punzi, Belloli, Gogny, Desfontis, & Mallem, ). Recently, a comparison between the vascular reactivity of the isolated bovine and equine digital artery was published (Zizzadoro et al., ). Although the endothelium‐dependent relaxation caused by the activation of endothelium muscarinic receptors has been described in the isolated bovine digital vein, the endothelium‐derived mediators of this classical endothelium‐dependent relaxation response remain to be characterized in this superficial venous vascular bed of the bovine digit.…”