title: The viscosity of fibrinogen subfractions and of EDTA denatured fibrinogen do not differ from that of native fibrinogen.
abstract: BACKGROUND
  Fibrinogen is a major determinant of plasma viscosity. The increased risk of atherothrombotic disease associated with a high fibrinogen concentration may partly be attributed to its effect on viscosity. Since the ratio between the three main fibrinogen subfractions high molecular weight (HMW)-, low molecular weight (LMW)-, and very low molecular weight (LMW')-fibrinogen is altered during acute phase conditions, and an increased HMW/LMW-fibrinogen ratio is associated with increased thromboembolic risk, we have examined how these subfractions affect viscosity. The viscosity of plasma is usually determined in ethylenediaminetetra-acetic acid (EDTA) plasma at 37 degrees C. Under such conditions the clotting properties of fibrinogen is affected due to denaturation. Denaturation of plasma proteins may affect their viscosity. Therefore, we have also investigated the effects of EDTA on the viscosity of fibrinogen.
  
  
  METHODS
  Purified fibrinogen was obtained by beta-alanine precipitation of plasma from healthy donors. Separation of the fibrinogen fractions was performed by gradual precipitation of purified fibrinogen by ammonium sulphate. The viscosity was determined using a Haake Microvisco 2 viscometer.
  
  
  RESULTS
  There was no statistically significant difference between the viscosity of native fibrinogen and the three fibrinogen subfractions. A substantial prolongation of the thrombin clotting time was observed in the fibrinogen solution containing EDTA at 37 degrees C compared to 20 degrees C. However, the viscosity of EDTA anticoagulated purified fibrinogen and plasma samples did not differ from that of heparin anticoagulated samples.
  
  
  CONCLUSIONS
  The viscosity of the main fibrinogen subfractions HMW-, LMW- and LMW-fibrinogen did not differ from that of native fibrinogen, and the use of EDTA as anticoagulant did not significantly affect the viscosity of fibrinogen at 37 degrees C.
authors.affiliation: Heart and Lung Center, Ullevål University Hospital, Kirkeveien 166, 0407 Oslo, Norway. Tors-jen@online.no
authors.forename: Torstein
authors.initials: T
authors.lastname: Jensen
authors.forename: Sigrun
authors.initials: S
authors.lastname: Halvorsen
authors.forename: Hans C
authors.initials: HC
authors.lastname: Godal
authors.forename: Per M
authors.initials: PM
authors.lastname: Sandset
authors.forename: Ole H
authors.initials: OH
authors.lastname: Skjønsberg
mesh_terms: D019343:Citric Acid / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D005340:Fibrinogen / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D011489:Protein Denaturation; D013696:Temperature; D013918:Thrombin Time; D014783:Viscosity
chemical_list: D010446:Peptide Fragments; D019343:Citric Acid; D005340:Fibrinogen; D006493:Heparin; D004492:Edetic Acid