ABSTRACT
Endothelin(ET) is known as a family of potent hydrophobic, vasoactive peptide. We investigated the effect according to the concentrations of ET on intraocular pressure(IOP), aqueous outflow facility, pupillary diameter and light reflex and iris vessels. Twenty-four hours after injection of 2.5 microgram and 10 microgram of ET-1 into the anteriorvitreous of rabbit eyes, the IOP was reduced by 69% and 80%, respectively and did not return to the level of prefreatment until at least 14 days and 20 days, respectively. But the decrease of IOP was not due to the increased aqueous outflow. The pupillary diameter of ET-1 treated eyes was 1 to 2mm larger than the pretreatment. The time course of the pupillary effects generally ran paralled with the reduction of IOP. The iridial and conjunctival hyperemia was detectable during the pupillary dilatation. Endothelins are therefore potential participants in the local regulation of IOP, ocular blood vessel tone, and iris smooth muscle tone.