In vitro studies on thrombin generation in citrated, r-hirudinized and heparinized whole blood.
The generation of thrombin in citrated, r-hirudinized and heparinized whole blood (final concentrations 10, 25, 50 micrograms/ml) was studied in the presence or absence of various activators. Whole blood from healthy volunteers was activated either by glass or dextran sulfate (contact activation; CA) as well as by thromboplastin/calcium chloride (extrinsic activation; EA) and by ellagic acid/cephaloplastin/calcium chloride (intrinsic activation; IA) and incubated 10 (CA, EA, IA) and 30 (CA) min at 37 degrees C. After the incubation period plasma levels of prothrombin fragment 1 + 2 (F1 + 2) and thrombin-antithrombin III complex (TAT) were measured utilizing ELISA methodology. After EA or IA no blood clotting occurred in all r-hirudinized samples and in heparinized blood at the highest concentration used. Despite inhibition of clotting F1 + 2 levels were increased both in r-hirudinized and in heparinized blood. However, in blood anticoagulated with heparin F1 + 2 levels after EA, IA and especially after CA were markedly lower than in r-hirudinized blood. Furthermore, in r-hirudinized blood an increase of TAT levels was found. The enhancement of F1 + 2 and TAT levels by r-hirudin was concentration-dependent and was lower in the higher r-hirudin concentration. The results indicate that in r-hirudinized whole blood significant amounts of thrombin can be generated which may elicit thrombin-mediated feedback mechanisms.
Kaiser
B
B
Institute of Pharmacology and Toxicology, Medical Academy of Erfurt, Germany.
Fareed
J
J
Walenga
J M
JM
Hoppensteadt
D
D
Markwardt
F
F
D001777:Blood Coagulation / Q000187:drug effects*; D001780:Blood Coagulation Tests; D002951:Citrates / Q000494:pharmacology; D019343:Citric Acid; D004305:Dose-Response Relationship, Drug; D006493:Heparin / Q000494:pharmacology; D006629:Hirudins / Q000494:pharmacology*; D006801:Humans; D010446:Peptide Fragments / Q000032:analysis*; D011516:Prothrombin / Q000032:analysis*; D011994:Recombinant Proteins / Q000494:pharmacology; D013917:Thrombin / Q000032:analysis*
D002951:Citrates; D006629:Hirudins; D010446:Peptide Fragments; D011994:Recombinant Proteins; C045879:prothrombin fragment 1.2; D019343:Citric Acid; D011516:Prothrombin; D006493:Heparin; D013917:Thrombin