Standardization of methods for measuring plasminogen activator inhibitor activity in human plasma.
We have standardized the measurement of plasminogen activator inhibitor type 1 (PAI-1) activity in plasma. One-chain tissue-type plasminogen activator (t-PA; EC 3.4.21.31; final activity, 5 int. units/mL) was incubated with plasma (final dilutions 1:4 to 1:40) in phosphate buffer (pH 7.4, ionic strength = 0.15) for 15 min at 37 degrees C, followed by acidification and measurement of residual t-PA activity by an amidolytic method. The PAI-1 activity assay was 98% specific for PAI-1 activity in samples from both pregnancy and nonpregnancy, and varied linearly with added plasma volume when the percent inhibition of t-PA was between 8% and 50%. For the standardized method, analytical recovery was 93 +/- 5%, the detection limit was 1.6 arbitrary units per milliliter (1 arb. unit of PAI-1 activity = inhibition of 1 int. unit of t-PA activity), and total imprecision was 10.2 (SD 0.7) arb. units/mL (CV = 7%, n = 20). The average PAI-1 activity in 10 healthy individuals drawn between 0800 and 1000 hours was 23.9 +/- 15.4 arb. units/mL. Compared with the standardized assay, two of three previously described assays underestimated PAI-1 activity in plasma by 77% and 85%, respectively.
Chandler
W L
WL
Department of Laboratory Medicine, University of Washington, Seattle 98195.
Loo
S C
SC
Nguyen
S V
SV
Schmer
G
G
Stratton
J R
JR
D001774:Blood Chemical Analysis / Q000592:standards; D002021:Buffers; D002863:Chromogenic Compounds; D003488:Cyanogen Bromide; D005260:Female; D006023:Glycoproteins / Q000097:blood* / Q000276:immunology; D006801:Humans; D006868:Hydrolysis; D010446:Peptide Fragments / Q000097:blood; D010960:Plasminogen Activators / Q000037:antagonists & inhibitors*; D015849:Plasminogen Inactivators; D011247:Pregnancy
D002021:Buffers; D002863:Chromogenic Compounds; D006023:Glycoproteins; D010446:Peptide Fragments; D015849:Plasminogen Inactivators; D010960:Plasminogen Activators; D003488:Cyanogen Bromide