Purchase this article with an account.
EA Polska, G Fuchsjaeger-Mayrl, A Luksch, M Wolzt, L Schmetterer; Role of endothelin in choroidal blood flow regulation of during isometric exercise in healthy humans. . Invest. Ophthalmol. Vis. Sci. 2002;43(13):842.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Endothelin and angiotensin are important regulators of vascular tone. Both peptides have been shown to play role in the control of ocular blood flow. Animal experiments indicate that endothelin is also involved in choroidal autoregulation, whereas little evidence exists for angiotensin. We hypothesized that blockade of the endothelinA (ETA)-receptor and/or angiotensin converting enzyme (ACE) inhibition may influence choroidal blood flow during isometric exercise in humans. Methods: To test this hypothesis we performed a randomized, double-masked, placebo-controlled, three way cross over study in 12 healthy male volunteers. Subjects received on different study days intravenous infusions of the ETA receptor antagonist BQ-123, the ACE inhibitor enalapril or placebo. During these infusion periods subjects performed squatting for 6 minutes. Choroidal blood flow was assessed with laser Doppler flowmetry and ocular perfusion pressure (OPP) was calculated from mean arterial pressure and intraocular pressure. Results: Neither BQ-123 nor enalapril altered resting OPP or basal choroidal blood flow. The relative increase in OPP during isometric exercise was comparable with all administered drugs. Isometric exercise increased choroidal blood flow during placebo and enalapril administration to a comparable degree. By contrast, administration of BQ-123 induced a more pronounced increase in choroidal blood flow during isometric exercise (p < 0.001 versus placebo). Conclusion: These data indicate that endothelin, but not angiotensin, plays an important role in the regulation of choroidal blood flow during isometric exercise. Based on our results we hypothesize that endothelin is one of the vasoconstrictors which is locally produced to allow for constant choroidal blood flow during moderate changes in ocular perfusion pressure.
This PDF is available to Subscribers Only