Non-anticoagulant heparin increases endothelial nitric oxide synthase activity: role of inhibitory guanine nucleotide proteins

J Mol Cell Cardiol. 1998 Dec;30(12):2669-82. doi: 10.1006/jmcc.1998.0831.


Heparin, which is widely used clinically, has recently been shown to have specific properties affecting the vascular endothelium. We hypothesized that heparin stimulates endothelial nitric oxide synthase (eNOS) activity by a mechanism independent of its anticoagulant properties and dependent on an inhibitory guanine nucleotide regulatory protein (Gi). We determined the effect of both heparin and N-acetyl heparin (Non-Hep), a heparin derivative without anticoagulant properties, on eNOS activity in cultured bovine aortic endothelial cells and on endothelium-dependent relaxation in isolated vascular rings. The eNOS activity was determined by measuring both citrulline and nitric oxide (NO) metabolite formation. Heparin and Non-Hep dose-dependently increased basal eNOS activity (ED50 1.0 microgram/ml or 0.15 U/ml), an effect that was significantly inhibited by pertussis toxin (100 ng/ml), a Gi-protein inhibitor. Agonist-stimulated (acetylcholine, 10 microM) eNOS activity was potentiated following pre-treatment with both heparin and Non-Hep and reversed by pertussis toxin. Heparin and Non-Hep induced a dose-dependent relaxation in preconstricted thoracic aortic rings, an effect that was significantly inhibited by pertussis toxin, endothelial inactivation (following treatment with sodium deoxycholate) and NG-nitro-L-arginine-methyl ester (L-NAME). We conclude that heparin and non-anticoagulant heparin induce endothelium-dependent relaxation following activation of eNOS by a mechanism involving a Gi-protein. Administration of heparin derivatives without anticoagulant properties may have therapeutic implications for the preservation of eNOS in conditions characterized by endothelial dysfunction.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylcholine / pharmacology
  • Animals
  • Aorta, Thoracic / physiology
  • Blotting, Western
  • Cattle
  • Cells, Cultured
  • Citrulline / pharmacology
  • Deoxycholic Acid / pharmacology
  • Dose-Response Relationship, Drug
  • Edetic Acid / pharmacology
  • Endothelium, Vascular / enzymology*
  • GTP-Binding Proteins / drug effects
  • GTP-Binding Proteins / physiology*
  • Heparin / analogs & derivatives
  • Heparin / pharmacology*
  • In Vitro Techniques
  • Male
  • NG-Nitroarginine Methyl Ester / pharmacology
  • Nitric Oxide Synthase / metabolism*
  • Pertussis Toxin
  • Potassium Chloride / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Time Factors
  • Virulence Factors, Bordetella / pharmacology


  • Virulence Factors, Bordetella
  • Deoxycholic Acid
  • N-acetylheparin
  • Citrulline
  • Potassium Chloride
  • Heparin
  • Edetic Acid
  • Nitric Oxide Synthase
  • Pertussis Toxin
  • GTP-Binding Proteins
  • Acetylcholine
  • NG-Nitroarginine Methyl Ester