Characterization and comparison of the responses of equine digital arteries and veins to endothelin-1.
OBJECTIVE
To compare the responses of equine digital arteries (EDAs) and equine digital veins (EDVs) to endothelin-1 (ET-1) and determine the role of the endothelium and type of receptors involved in the modulation and mediation of those responses, respectively.


METHODS
5 to 9 palmar digital vessels/experiment from 28 healthy horses.


METHODS
Rings of dissected vessels were mounted under tension between force transducer wires in organ baths containing Krebs-Henseleit solution at 30 degrees C. Responses of EDAs and EDVs (with intact [+e] or denuded [-e] endothelium) to cumulative concentrations of ET-1 (10(-10) to 3 X 10(-7) M) were compared. For (+e)EDAs and (+e)EDVs precontracted with a thromboxane-mimetic (U44069; 10(-8) M) and (-e)EDAs and (-e)EDVs, responses to an ETB receptor agonist (S6c; 10(-10) to 3 X 10(-7) M) were evaluated. Responses to ET-1 (10(-7) M) in (-e)EDAs and (-e)EDVs were evaluated after incubation with an ETA receptor antagonist (BQ-123; 3 X 10(-7) M), an ETB receptor antagonist (BQ-788; 3 X 10(-7) M), or vehicle solution.


RESULTS
Endothelin-1 induced a concentration-dependent contraction of endothelium-intact and -denuded EDAs and EDVs; EDVs were more sensitive. Neither vessel type relaxed in response to S6c, although 2 of the (-e)EDAs contracted mildly. Whereas BQ-123 inhibited the (-e)EDA and (-e)EDV responses to ET-1, BQ-788 had no effect.


CONCLUSIONS
Endothelin-1 induced digital vasoconstriction (marked constriction in veins). This action was unaffected by endothelium and mediated predominantly by ETA receptors. These findings suggest ET-1 can induce selective digital venoconstriction.
Katz
Lisa M
LM
Department of Veterinary Clinical Sciences, University of London, The Royal Veterinary College, North Mymms, Hertfordshire AL9 7TA, United Kingdom.
Marr
Celia M
CM
Elliott
Jonathan
J
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology*; D006736:Horses / Q000502:physiology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D014034:Toes / Q000098:blood supply*; D014680:Veins / Q000187:drug effects / Q000502:physiology*
D019332:Endothelin-1