Summary
Functional assay of extrinsic (tissue-type) plasminogen activator (EPA) in plasma
on fibrin plates was evaluated. Using specific quenching antibodies, we demonstrated
the method to be specific for EPA under all conditions tested. Contributions of urokinases
and intrinsic activators were excluded. The quantity of EPA in blood samples, as compared
with purified uterine tissue activator, shows 1 blood activator unit (BAU) to be comparable
to 0.93 ng.
The median values for EPA activity for healthy volunteers were: baseline, 1.9 BAU/ml
(n = 123); diurnal, 5.5 BAU/ml (n = 12); DDAVP administration, 11.7 BAU/ml (n = 39);
exhaustive exercise, 25 BAU/ml (n = 24); venous occlusion (15 min), 35 BAU/ml (n =
61). A large inter-individual variation in EPA activity was found, while individual
baseline values tended to be constant for periods of weeks.
In vitro in blood EPA activity shows a disappearance of 50% in about 90 min at 37°
C; EPA activity in euglobulin fractions is stable for ≤2 hr at 37° C.
A rapid decrease in EPA activity occurs in vivo, as noted after extracorporal circulation
and exercise stimulation (t½ decay, 2-5 min).
Keywords
Extrinsic (tissue-type) plasminogen activator - DDAVP - Venous occlusion - Fibrin
plate
