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Abstract #8443 Published in IGR 5-1
Role of endothelin-1 in choroidal blood flow regulation during isometric exercise in healthy humans
Fuchsjager-Mayrl G; Luksch A; Malec M; Polska E; Wolzt M; Schmetterer LInvestigative Ophthalmology and Visual Science 2003; 44: 728-733
PURPOSE: There is evidence that the choroid has some autoregulatory capacity in response to changes in ocular perfusion pressure (OPP). The mediators of this response are as yet unidentified. The hypothesis for the current study was that endothelin (ET)-1 and/or angiotensin (ANF)-II may be involved in choroidal vasoconstriction during an increase in OPP. METHODS: To test this hypothesis a randomized, double-masked, placebo-controlled, three-way crossover study was performed in 12 healthy male volunteers. Subjects received on different study days intravenous infusions of the specific ET(A) receptor antagonist BQ-123, the angiotensin converting enzyme inhibitor enalapril or placebo. During these infusion periods subjects were asked to squat for six minutes. Choroidal blood flow was measured using a confocal laser Doppler flowmeter and ocular perfusion pressure (OPP) was calculated from mean arterial pressure and intraocular pressure (IOP). RESULTS: BQ-123 and enalapril had no effect on basal blood pressure, pulse rate, IOP, or choroidal blood flow. During isometric exercise, a pronounced increase in mean arterial pressure paralleled by an increase in OPP was observed. Although choroidal blood flow slightly increased during squatting, the increase was much less pronounced than the increase in OPP, indicating some regulatory potential of the choroid. Enalapril did not alter the choroidal pressure-flow relationship during isometric exercise, but BQ-123 induced a significant leftward shift of the pressure-flow curve (p < 0.001). CONCLUSIONS: The present data indicate that ET-1, but not ANG II, plays a role in choroidal blood flow regulation during isometric exercise in healthy humans. Hence, impaired choroidal autoregulation in patients with ocular vascular diseases may arise from an altered endothelin system. Further studies in such patients are warranted to verify this hypothesis.
Dr. G. Fuchsjager-Mayrl, Department of Clinical Pharmacology, University of Vienna, Vienna, Austria
Classification:
6.11 Bloodflow measurements (Part of: 6 Clinical examination methods)
