ROLE OF THE ENDOTHELIUM IN MODULATING FUNCTIONAL-RESPONSES OF ISOLATED BOVINE ANTERIOR CILIARY ARTERIES TO VASOCONSTRICTOR AGONISTS

Background/aims-Endothelium dependent vasodilatation is an important r egulator of blood flow to the eye but its role has not been investigat ed in vessels supplying the ciliary body. This study assessed the role of the endothelium in modulating vasoconstrictor responses of the int raocular bovine anterior ciliary artery. Methods-Bovine anterior cilia ry arteries (n=33) were mounted in a myograph, containing physiologica l salt solution at 37 degrees C, for isometric force measurement. Cumu lative concentration-response curves were obtained to the constrictor agonists 5-hydroxytryptamine (5-HT), noradrenaline, phenylephrine, pro staglandin F-2u, endothelin-l, and KCl in both endothelium intact and denuded arteries. Results-All vasoconstrictors produced sustained cont ractile responses which were unaffected by the removal of the endothel ium. Responses to 5-HT were also unaffected by inhibition of nitric ox ide synthase. Conclusion-These results indicate that neither agonist s timulated nor basal release of nitric oxide from the endothelium modul ates responses to vasoconstrictor agonists in the isolated bovine ante rior ciliary artery when measured in a no flow isometric system.