Document Detail


ETa-receptor blockade, but not ACE inhibition, blunts retinal vessel response during isometric exercise.
MedLine Citation:
PMID:  16327016     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Angiotensin II and endothelin-1 are potent vasoconstrictors that appear to play a role in retinal blood flow regulation. In the present study, we investigated the possible role of the angiotensin and the endothelin system in the regulation of retinal vessel diameters during isometric exercise in healthy humans. The study design was randomized, double-masked, placebo-controlled, and three-way cross over. Twelve healthy subjects performed squatting exercises for 6 min during infusion of either an angiotensin-converting enzyme 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 noninvasively, and intraocular pressure was measured with applanation tonometry. Squatting induced a significant increase in blood pressure and pulse rate, which was paralleled by a vasoconstriction in retinal arteries and veins. Intraocular pressure was only slightly increased during the squatting periods. BQ-123 significantly blunted the exercise-induced decrease in venous (P < 0.01) and arterial (P < 0.02, ANOVA) vessel diameters but had no effect on basal retinal diameters. By contrast, enalapril did neither influence vessel diameter at baseline conditions nor in response to isometric exercise. The data of the present study indicate that retinal vasoconstriction during isometric exercise is modified by ET(A)-receptor blockade, whereas it is not altered by angiotensin-converting enzyme inhibition. Hence, the present data indicate that endothelin-1, but not angiotensin II, is involved in retinal blood flow regulation during isometric exercise.
Authors:
Alexandra Luksch; Barbara Wimpissinger; Kaija Polak; Kerstin Jandrasits; Leopold Schmetterer
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Publication Detail:
Type:  Journal Article; Randomized Controlled Trial     Date:  2005-12-03
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  290     ISSN:  0363-6135     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2006 Apr 
Date Detail:
Created Date:  2006-03-15     Completed Date:  2006-05-02     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  H1693-8     Citation Subset:  IM    
Affiliation:
Dept. of Clinical Pharmacology, University of Vienna, A-1090 Vienna, Austria.
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MeSH Terms
Descriptor/Qualifier:
Adult
Angiotensin II / metabolism*
Angiotensin-Converting Enzyme Inhibitors / administration & dosage
Cross-Over Studies
Double-Blind Method
Enalapril / administration & dosage
Endothelin-1 / metabolism*
Exercise Test
Female
Humans
Isometric Contraction / drug effects,  physiology*
Male
Peptides, Cyclic / administration & dosage
Physical Exertion / physiology
Placebo Effect
Receptor, Endothelin A / antagonists & inhibitors,  metabolism*
Retinal Vessels / drug effects,  physiology*
Vasoconstriction / drug effects,  physiology*
Chemical
Reg. No./Substance:
0/Angiotensin-Converting Enzyme Inhibitors; 0/Endothelin-1; 0/Peptides, Cyclic; 0/Receptor, Endothelin A; 11128-99-7/Angiotensin II; 136553-81-6/cyclo(Trp-Asp-Pro-Val-Leu); 75847-73-3/Enalapril

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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