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Evidence for endothelium-derived relaxing factor/nitric oxide in equine digital arteries
A M Cogswell1, P J Johnson, H R Adams
1Department of Veterinary Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia 65211, USA.
Objective:
To test the hypothesis that endothelium-derived nitric oxide modulates vasomotor reactivity in equine digital arteries.
Design:
Digital arteries were isolated from adult horses, and their vasodilator properties were examined in an in vitro controlled environment.
Animals:
Five adult horses (1 gelding, 4 mares) without evidence of hoof or vascular disease were studied.
Procedure:
Arterial rings with or without endothelium were exposed to endothelium-dependent vasodilator drugs in the presence or absence of a pharmacologic inhibitor of the enzyme nitric oxide synthase.
Results:
Vasodilator effects of 3 endothelium-dependent vasorelaxant agents were significantly greater in endothelium-intact vessels than in endothelium-denuded vessels. Moreover, a nitric oxide synthase inhibitor reduced vasodilator responses to endothelium-dependent vasodilators in endothelium-intact arteries, but had no discernable effects in endothelium-denuded arteries.
Conclusions:
These findings indicate the presence of endothelium-derived relaxing factor/nitric oxide in blood vessels of horses, and identify vascular endothelium as an endogenous modulator of vasomotor tone in the digital arteries of this species.