title: Method for the determination of fast acting plasminogen activator inhibitor capacity (PAI-cap) in plasma, platelets and endothelial cells.
abstract: A titration assay for the determination of the fast acting plasminogen activator inhibitor capacity (PAI-cap) was developed. Most of the hitherto published assays for fast acting PAI are reported to have the disadvantage of non-parallel titration curves of tissue plasminogen activator (t-PA) in buffer and plasma. In the assay reported here, this problem has been overcome by adequate predilution of the samples, thus achieving parallel titration curves regardless of the individual PAI-cap of a sample. Provided that values are calculated from parallel titration curves, reproducible PAI-cap values at different dilutions of a sample are obtained. This assay can be applied for the determination of PAI-cap in plasma, serum and other biological fluids as platelet releasates and endothelial cell conditioned medium. PAI-cap of plasma of 10 healthy male volunteers ranged from 15.3 to 32.3 arbitrary inhibitor units AU/ml (24.5 +/- 5.2, mean +/- SD). The alternative use of three different anticoagulants (citrate, EDTA, heparin) had no influence on PAI-cap determinations. Serum generated from blood contained a mean of PAI-cap of 129% in comparison to the plasma of the same donor indicating the release of PAI from cells during clotting. Plasma PAI-cap changed during the day with a constant decrease from the highest levels in the morning (100%) to low levels in the evening (62.9%). Platelets aggregated by thrombin released plasminogen activator inhibitor amounting to a mean PAI-cap of 4.33 +/- 2.98 AU per 2.5 X 10(8) cells.
mesh_terms: D000925:Anticoagulants / Q000494:pharmacology; D001792:Blood Platelets / Q000032:analysis*; D002478:Cells, Cultured; D004727:Endothelium / Q000032:analysis*; D006801:Humans; D008722:Methods; D014471:Umbilical Veins
chemical_list: D000925:Anticoagulants