The effects of intravitreally injected endothelin-1 on the iris-ciliary body microvasculature in rabbits.
OBJECTIVE
We previously reported that intravitreal injection of 0.5 microg of endothelin-1 (ET-1) caused both a sustained reduction of intraocular pressure (IOP) and decreased aqueous production in the rabbit eye. On the theory that these effects might have resulted from a sustained reduction of blood flow to the ciliary body due to ET-1-mediated vasoconstriction, in the present study we attempted to determine if ET-1 causes any changes in the vascular caliber of the iris-ciliary body.


METHODS
ET-1 solution (0.5 microg) was injected into the vitreous of one eye of each of 10 albino rabbits; the same amount of vehicle was injected into the contralateral eyes. One h following these injections in five of the rabbits and 24 h following them in the other five rabbits, ocular microvascular castings were obtained under controlled physiologic conditions, and the amount of vasoconstriction of the arterioles branching from the major arterial circle of the iris (MAC) and supplying the iris-ciliary body was measured by a scanning electron microscope and expressed as a percentage.


RESULTS
The ET-1 caused a statistically significant focal vasoconstriction in the treated eyes as compared with the contralateral, control eyes (9.9% at 1 h and 6.2% at 24 h; both P = . 0001).


CONCLUSIONS
Intravitreally injected ET-1 caused statistically significant, but only mild vasoconstriction of the arterioles supplying the ciliary processes.
Sugiyama
K
K
Department of Ophthalmology, Gifu University School of Medicine, 40 Tsukasamachi, Gifu-City 500, Japan.
Haque
M S
MS
Onda
E
E
Taniguchi
T
T
Kitazawa
Y
Y
D000818:Animals; D001082:Aqueous Humor / Q000187:drug effects / Q000502:physiology; D002924:Ciliary Body / Q000098:blood supply* / Q000187:drug effects*; D016319:Corrosion Casting; D016232:Endothelins / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007267:Injections; D007429:Intraocular Pressure / Q000187:drug effects; D007498:Iris / Q000098:blood supply* / Q000187:drug effects*; D008297:Male; D008833:Microcirculation / Q000033:anatomy & histology / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D011817:Rabbits; D014661:Vasoconstriction / Q000187:drug effects; D014822:Vitreous Body
D016232:Endothelins