Influence of ACE-inhibition and ETA-receptor Blockade on Retinal Vessel Response to Isometric Exercise

Abstract

Abstract: : Purpose: Angiotensin II and endothelin-1 are potent vasoconstrictors which appear to play a role in retinal blood flow regulation. Our aim was to investigate a possible influence of the angiotensin and the endothelin (ET) system in the regulation of retinal vessel diameters during isometric exercise in healthy humans. Methods: The study design was randomized, double masked, placebo-controlled and 3-way cross-over. 12 healthy subjects performed squatting for 6 minutes during infusion of either an ACE-inhibitor (enalapril), an ET_A-receptor antagonist (BQ-123) or placebo. Retinal vessel diameters were measured continuously with the Zeiss retinal vessel analyzer. Systemic hemodynamics were assessed non-invasively and intraocular pressure was measured with applanation tonometry. Results: Squatting induced a significant increase in blood pressure and pulse rate, which was paralleled by a vasoconstriction in retinal venous and arterial diameters. BQ-123 significantly blunted the exercise-induced decrease in venous and arterial vessel diameters (p<0.01) whereas enalapril did not influence vessel diameter. Intraocular pressure was only slightly increased during the squatting periods. Conclusions: The data of the present study indicate that retinal vasoconstriction during isometric exercise is significantly altered by ET_A-receptor blockade whereas it is not altered by ACE-inhibition.

Keywords: pharmacology • retina