title: Reduced contribution of endothelin to the regulation of systemic and pulmonary vascular tone in severe familial hypercholesterolaemia.
abstract: Vascular dysfunction has been associated with familial hypercholesterolaemia (FH), a severe form of hyperlipidaemia. We recently demonstrated that swine with FH exhibit reduced exercise-induced systemic, but not pulmonary, vasodilatation involving reduced nitric oxide (NO) bioavailability. Since NO normally limits endothelin (ET) action, we examined the hypothesis that reduced systemic vasodilatation during exercise in FH swine results from increased ET-mediated vasoconstriction. Systemic and pulmonary vascular responses to exercise were examined in chronically instrumented normal and FH swine in the absence and presence of the ETA/B receptor antagonist tezosentan. Intrinsic reactivity to ET was further assessed in skeletal muscle arterioles. FH swine exhibited ∼9-fold elevation in total plasma cholesterol versus normal swine. Similar to our recent findings, systemic, not pulmonary, vasodilatation during exercise was reduced in FH swine. Blockade of ET receptors caused marked systemic vasodilatation at rest and during exercise in normal swine that was significantly reduced in FH swine. The reduced role of ET in FH swine in vivo was not the result of decreased arteriolar ET responsiveness, as responsiveness was increased in isolated arterioles. Smooth muscle ET receptor protein content was unaltered by FH. However, circulating plasma ET levels were reduced in FH swine. ET receptor antagonism caused pulmonary vasodilatation at rest and during exercise in normal, but not FH, swine. Therefore, contrary to our hypothesis, FH swine exhibit a generalised reduction in the role of ET in regulating vascular tone in vivo probably resulting from reduced ET production. This may represent a unique vascular consequence of severe familial hypercholesterolaemia.
authors.affiliation: Experimental Cardiology, Thoraxcenter, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands.  d.merkus@erasmusmc.nl.
authors.forename: Shawn B
authors.initials: SB
authors.lastname: Bender
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: de Beer
authors.forename: Darla L
authors.initials: DL
authors.lastname: Tharp
authors.forename: Elza D
authors.initials: ED
authors.lastname: van Deel
authors.forename: Douglas K
authors.initials: DK
authors.lastname: Bowles
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: Duncker
authors.forename: M Harold
authors.initials: MH
authors.lastname: Laughlin
authors.forename: Daphne
authors.initials: D
authors.lastname: Merkus
mesh_terms: D000818:Animals; D001160:Arterioles / Q000378:metabolism / Q000502:physiology; D065128:Endothelin Receptor Antagonists / Q000494:pharmacology; D016232:Endothelins / Q000097:blood*; D006937:Hypercholesterolemia / Q000151:congenital / Q000378:metabolism* / Q000503:physiopathology; D008168:Lung / Q000098:blood supply*; D018482:Muscle, Skeletal / Q000098:blood supply*; D005082:Physical Exertion; D011725:Pyridines / Q000494:pharmacology; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism; D013552:Swine; D013556:Swine, Miniature; D013777:Tetrazoles / Q000494:pharmacology; D014664:Vasodilation
chemical_list: D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D011725:Pyridines; D017466:Receptors, Endothelin; D013777:Tetrazoles; C120582:tezosentan