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Role of Endothelium and Nitric Oxide in the Response of Equine Colonic Arterial Rings to Vasoconstrictor Agents
Author(s) -
VENUGOPALAN CHANGARAM S.,
MOORE RUSTIN M.,
HOLMES EARNESTINE P.,
SEDRISH STEVEN A.
Publication year - 1997
Publication title -
veterinary surgery
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 79
eISSN - 1532-950X
pISSN - 0161-3499
DOI - 10.1111/j.1532-950x.1997.tb01482.x
Subject(s) - medicine , endothelium , nitric oxide , histamine , norepinephrine , vasodilation , vasoconstriction , endocrinology , angiotensin ii , serotonin , perfusion , thromboxane , anesthesia , blood pressure , receptor , dopamine , platelet
Objective‐ To determine the in vitro contractile responses of equine colonic arteries to angiotensin II, histamine, serotonin, norepinephrine, prostaglandin F 2α , vasopressin, and a thromboxane‐B 2 ‐analogue. Study Design‐ The tension generated in colonic arterial rings placed in organ baths with oxygenated Tyrode's solution at 37°C after exposure to the previously mentioned chemical agents was measured using force‐transducers interfaced with a polygraph. Sample Population‐ Large colon arterial rings collected from eight horses. Methods‐ The rings were allowed to equilibrate for 45 minutes after applying 2 g tension. Bath solution was replaced and tension reapplied at 15‐minute intervals. Cumulative‐concentration‐responses were determined for concentrations ranging from 10 ‐8 M to 10 ‐4 M on three vessel groups namely endothelium intact, endothelium denuded, and L‐NAME treated. The maximal response for each vessel was considered as 100%; responses to lower concentrations were calculated as a percentage of the maximum. The EC 50 value was determined for each concentration‐response relationship of each agent. Results‐ Vessels with denuded endothelium or those incubated with L‐NAME had greater contractile responses. Angiotensin, histamine, serotonin, and norepinephrine produced greater maximal responses than the other agents. Endothelium denuded rings had lower EC 50 values. Responses to norepinephrine and serotonin were affected less by denudation. Conclusion‐ Endothelium plays an important role in modulating responses of colonic arterial rings to contractile agents. Endothelium‐derived vasodilators, other than nitric oxide, may modulate contractile responses of equine colonic arteries. Clinical Relevance‐ Endothelial damage associated with colonic vovulus may be a major factor for sustained reduced perfusion after surgical correction.