[Effects of endothelin on retinal blood vessels].

Endothelins (ETs), which are one of the most potent vasoconstrictors, were discovered in 1988. ETs are involved in the regulation of vascular smooth muscle and are thought to function like a local hormone. In this study, we measured changes in the caliber of retinal blood vessels caused by the intravitreal injection of ET 1 in rabbits, using fundus photography. The retinal artery showed an immediate vasoconstriction after the injection (0.1 ml) of ET 1 at 10(-6)M. However, ET 1 in lower concentrations (10(-7)M and 10(-8)M) caused vasodilations initially and subsequently vasoconstrictions. A dose-response relation was found. The blood vessel caliber reduced maximumly to 53% the value before injection. The vasoconstriction due to ET 1 may induce retinal ischemia and hypoxia. We speculate that ET 1 may be involved in the regulation of retinal blood vessels.