title: Vascular effects of endothelin-1 in humans and influence of calcium channel blockade.
abstract: OBJECTIVE
  To investigate the effects of brachial artery infusions of endothelin-1 on forearm blood flow in normal healthy volunteers.
  
  
  METHODS
  Brachial artery cannulation was used for a direct assessment of blood pressure and for intra-arterial regional drug infusions. Drug-induced forearm blood flow changes were measured by venous occlusion plethysmography.
  
  
  RESULTS
  Low-dose endothelin-1 infusions resulted in a significant increase in forearm blood flow, indicating vasodilation, which was significantly attenuated by cyclo-oxygenase inhibition using aspirin. High-dose endothelin-1 infusions resulted in transient vasodilation, followed by dose-dependent and long-lasting vasoconstriction. In the human forearm the vasoconstrictor potency of endothelin-1 was approximately 10-15 times greater than that of norepinephrine. Maximal cyclic GMP-dependent vascular muscle relaxation, after muscarinergic stimulation by acetylcholine (endothelium-dependent) or after infusion of sodium nitroprusside (endothelium-independent), did not prevent endothelin-1 induced vasoconstriction. However, calcium channel blockade by brachial artery infusions of maximally vasodilating doses of either verapamil or nifedipine not only abolished the endothelin-induced vasoconstriction but also unmasked the vasodilator potency of high-dose endothelin-1 infusions. The infusion of lower doses of nifedipine indicated that endothelin-1 induced vasoconstriction was reversed by plasma concentrations estimated to be in the therapeutic range.
  
  
  CONCLUSIONS
  These results demonstrate a dual action of luminally applied endothelin-1 in human resistance vessels in vivo, consisting of transient initial vasodilation followed by pronounced vasoconstriction, and suggest that blockade of voltage-operated calcium channels can effectively counter the vasoconstrictor effects of endothelin-1.
authors.affiliation: Department of Medicine, University Hospital, Basel, Switzerland.
authors.forename: W
authors.initials: W
authors.lastname: Kiowski
authors.forename: L
authors.initials: L
authors.lastname: Linder
authors.forename: P
authors.initials: P
authors.lastname: Erne
mesh_terms: D000328:Adult; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D016232:Endothelins / Q000494:pharmacology*; D005260:Female; D005542:Forearm / Q000098:blood supply; D006801:Humans; D008297:Male; D012039:Regional Blood Flow / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D002121:Calcium Channel Blockers; D016232:Endothelins