Document Detail

Role of Endothelin-A receptors in optic nerve head red cell flux regulation during isometric exercise in healthy humans.
MedLine Citation:
PMID:  23103498     Owner:  NLM     Status:  Publisher    
Endothelin-1 (ET-1) is an important regulator of vascular tone in the eye. It appears to play a role in ocular disease, because of its strong vasoconstrictor action, its role in intraocular pressure homeostasis, and its neurotoxic potential. We have previously shown that ET-1 is involved in choroidal red cell flux (RCF) regulation during isometric exercise in healthy humans. In the present study we hypothesized that ET-1 also plays a role in optic nerve head (ONH) RCF regulation during isometric exercise. To test this hypothesis we performed a randomized, double-masked, placebo-controlled, two way crossover study in 15 healthy volunteers. Subjects were randomized to receive intravenous infusions of the specific ET(A) receptor antagonist BQ-123 and placebo on two different study days. During these infusion periods subjects performed squatting for 6 minutes to increase ocular perfusion pressure (OPP). ONH RCF was assessed with laser Doppler flowmetry and OPP was calculated from mean arterial pressure and intraocular pressure. BQ-123 did not change OPP or ONH RCF at baseline. The relative increase in OPP during isometric exercise was comparable between both groups (between 84% and 88 %, p = 0.76 between groups; p < 0.001 versus baseline). Isometric exercise increased ONH RCF during placebo and BQ-123, but the increase was more pronounced when the ET(A) receptor antagonist was administered (placebo: 27.3 ± 5.4 %; BQ-123: 39.2 ± 4.4 %; p = 0.007 between groups). The present data indicate that ET-1 regulates red cell flux in the ONH beyond the autoregulatory range.
Agnes Boltz; Doreen Schmidl; René M Werkmeister; Michael Lasta; Semira Kaya; Stefan Palkovits; Reinhard Told; Sophie Frantal; Gerhard Garhöfer; Leopold Schmetterer
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-26
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  -     ISSN:  1522-1539     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-29     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1Medical University of Vienna.
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