Effect of PAI-1 levels on the molar concentrations of active tissue plasminogen activator (t-PA) and t-PA/PAI-1 complex in plasma

Abstract

We determined the in vivo molar concentrations of active tissue plasminogen activator (t-PA), active plasminogen activator inhibitor type 1 (PAI-1), and t-PA/PAI-1 complex. t-PA activity was measured in plasma stabilized by immediate acidification. PAI-1 activity and t- PA/PAI-1 complex antigen were measured in citrated plasma; these measurements were corrected for the loss in PAI-1 activity and increase in complex that occurs in unacidified plasma samples due to the continued reaction between t-PA and PAI-1 after the sample was drawn. To convert t-PA and PAI-1 activity measurements into molar concentrations we determined the specific molar activity of t-PA and PAI-1 in vivo: 4.48 x 10(13) IU/mol. Of 72 subjects studied, 13 had less than 150 pmol/L active PAI-1; in these individuals 33% +/- 21% of their t-PA was active and the molar ratio of active t-PA to active PAI- 1 was 0.20 +/- 0.13. In the 11 subjects with greater than 500 pmol/L active PAI-1, 1.5% = 1.1% of the t-PA was active and the molar ratio of active t-PA to active PAI-1 was 0.0043 +/- 0.0036. Overall, the fraction of active t-PA declined exponentially as a function of the active PAI-1 concentration. During the day, the percentage of total t- PA that was active increased from 12% at 8:00 AM to 31% at 8:00 PM, while the molar ratio of active t-PA to active PAI-1 increased from 0.05 to 0.22 from morning to evening (n = 12).

The Effects of Chronic Smoking on the Fibrinolytic Potential of Plasma and Platelets

“…Despite such variation, the level of plasma PAI-1 exceeded that of t-PA in almost all subjects. Furthermore, the very close correlation between PAI-1 and t-PA suggests that mechanisms exist to maintain a relative balance between activator and inhibitor, in keeping with the findings of Chandler et al (1990). PAI-1 and t-PA have molecular masses of 48 kD and 65 kD respectively, and as PAI-1 and t-PA form a 1 : 1 stoichiometric complex (Booth, 1994), our data indicate that there was sufficient t-PA to overcome plasma PAI-1 in only one of the 54 subjects studied (a non-smoker).…”

Low serum BDNF may indicate the development of PSD in patients with acute ischemic stroke

“…Although no previous studies have investigated the direct relationship between the serum BDNF and tPA, a recent experimental study shows that tPA converts proBDNF to mBDNF by activating the extracellular protease plasmin, and application of mBDNF can completely rescue the L-LTP deficit in tPA knock-out mice (Pang et al, 2004), demonstrating a potential link between BDNF and tPA. Furthermore, total tPA antigen is a measure of inactive tPA/PAI-1 complex and free-active tPA (Chandler et al, 1990), and elevated total tPA antigen can reflex reduced net fibrinolytic capacity with relative excess in PAI-1 (Chandler et al, 1990;Chandler et al, 1997). So the increased serum tPA observed in this study likely reflects decreased serum free-active tPA.…”

Laboratory and clinical aspects of inherited thrombotic disorders

“…t-PA deficiency and excess fibrinolytic inhibitors. Recent data demonstrates that sample collection and timing are critical in the detection of patients with these fibrinolytic disorders [45][46][47][48]. For example, t-PA activity is unstable in normal plasma; for optimal measurements, citrated blood must be immediately acidified and the red blood cells rapidly removed before hemolysis occurs [45].…”