title: Collagen/endogenous thrombin-induced platelet aggregation in whole blood samples.
abstract: The aim of the study was to investigate the individual and combined effects of collagen (3.5 microg/ml) and endogenously generated thrombin (due to addition of 0.35 pmol/l tissue factor) on platelet aggregation in the physiological environment of whole blood by means of the impedance method. Lag times were significantly shorter when a combination of collagen and endogenous thrombin was used to provoke platelet aggregation (41.9 +/- 16.3 s) compared with collagen (173.8 +/- 52.1 s, P < 0.0001) or endogenous thrombin (94.3 +/- 43.6 s, P < 0.001). Amplitudes and slopes were the lowest in collagen-induced experiments (2.83 +/- 1.59 Omega and 1.79 +/- 0.45 Omega/min, respectively), whereas they were approximately the same in endogenous thrombin-induced experiments whether collagen was present or not (13.7 +/- 3.1 versus 11.2 +/- 4.0 Omega and 6.3 +/- 2.8 versus 5.6 +/- 2.3 Omega/min, respectively). No synergistic effect of collagen and endogenous thrombin on the clot formation process was observed by means of thrombelastometry. Moreover, thrombin potentials in tissue factor-activated plasma samples were approximately the same whether collagen was present or not (834 +/- 67 versus 809 +/- 63 nmol/l.min). In conclusion, endogenously generated thrombin is a potent platelet agonist in whole blood, and a combination of collagen and endogenous thrombin synergistically shortens the lag time until the onset of platelet aggregation.
authors.affiliation: Institute of Physiological Chemistry, Medical University of Graz, Graz, Austria. gerhard.cvirn@meduni-graz.at
authors.forename: Gerhard
authors.initials: G
authors.lastname: Cvirn
authors.forename: Siegfried
authors.initials: S
authors.lastname: Gallistl
authors.forename: Joerg
authors.initials: J
authors.lastname: Kutschera
authors.forename: Thomas
authors.initials: T
authors.lastname: Wagner
authors.forename: Ulrika
authors.initials: U
authors.lastname: Ferstl
authors.forename: Gunther
authors.initials: G
authors.lastname: Jurgens
authors.forename: Martin
authors.initials: M
authors.lastname: Koestenberger
mesh_terms: D000328:Adult; D001777:Blood Coagulation / Q000502:physiology; D003094:Collagen / Q000502:physiology*; D006801:Humans; D008297:Male; D010974:Platelet Aggregation / Q000502:physiology*; D013916:Thrombelastography / Q000379:methods; D013917:Thrombin / Q000502:physiology*
chemical_list: D003094:Collagen; D013917:Thrombin