The response of retinal vasculature to angiotensin.

A retinal arterial constriction was produced in anesthetized cats with a continuous transvitreal infusion of angiotensin I or angiotensin II (Ile-5). Constriction of vessels near the infusion cannula tip occurred over a range of angiotensin II concentrations from 10(-9) to 10(-4) molar, and was reversibly blocked by a ten-fold excess of the competitive antagonist saralasin. Constriction did not occur in response to angiotensin I if angiotensin-converting enzyme was blocked with Captopril. Control infusions of saline did not elicit a contraction of the retinal arteries. Severe axonal and inner retinal damage and necrosis occurred when angiotensin II produced a prolonged vasospasm, but not after infusion with control solutions, or when-constriction caused by angiotensin was brief.