Characterization with a simple clotting assay of the tissue factor inhibiting activity in serum.
The serum inhibiting activity on tissue factor (TFI) was evaluated as follows: normal human serum was incubated at room temperature with highly diluted rabbit brain thromboplastin (TF) and calcium ions; after 30 min. rabbit brain cephalin, calcium and normal human plasma were added to a small aliquot of TF/serum mixture; the clotting time at 37 degrees C was then recorded. With this assay TFI activity is proportional to the serum level; it is low for incubation periods shorter than 30 min., is missing at TF concentrations higher than 8%, is strictly connected to the presence of F VII and F Xa in the serum sample, depends upon the presence of calcium ions and finally, is independent of antithrombin III. This inhibiting activity also seems to be saturable and reversible.
Cassetti
M
M
Servizio di Immunoematologia e Trasfusionale, Ospedale Civile, Terni, Italy.
Minestrini
D
D
Palazzesi
G
G
D000818:Animals; D000990:Antithrombin III / Q000032:analysis; D001780:Blood Coagulation Tests; D001790:Blood Physiological Phenomena; D002118:Calcium / Q000494:pharmacology; D005167:Factor VII / Q000032:analysis; D015951:Factor Xa / Q000032:analysis; D006801:Humans; D010714:Phosphatidylethanolamines / Q000494:pharmacology; D011817:Rabbits; D013925:Thromboplastin / Q000037:antagonists & inhibitors*
D010714:Phosphatidylethanolamines; D000990:Antithrombin III; D005167:Factor VII; D013925:Thromboplastin; D015951:Factor Xa; D002118:Calcium