Sensitive and direct assays for functionally active plasminogen activators (tissue-type and urokinase-type) in plasma

Area of Science:

• Biochemistry
• Hematology
• Physiology

Background:

• Established bioimmunoassays for tissue-type plasminogen activator (t-PA) and urinary-type plasminogen activator (U-PA) were modified for enhanced sensitivity.
• U-PA is also known as urokinase (UK).

Purpose of the Study:

• To develop sensitive and quantitative bioimmunoassays for t-PA and U-PA.
• To investigate the role of t-PA and U-PA in fibrinolytic activity changes after exercise.
• To examine the relationship between t-PA and U-PA levels and deep venous thrombosis (DVT).

Main Methods:

• Modified existing bioimmunoassays to achieve sensitivity ranges of 5-500 IU/L for t-PA and 5-500 X 10(-1) IU/L for U-PA.
• Compared the new t-PA assay with the traditional euglobulin clot lysis time (ECLT) assay.
• Measured t-PA and U-PA levels in plasma samples from subjects after exercise and during venous occlusion, with and without DVT.

Main Results:

• The new t-PA assay is a quantitative alternative to ECLT, showing high correlation coefficients (0.967 and 0.914).
• Exercise-induced enhanced fibrinolytic activity is due to increased t-PA, while U-PA levels remain unchanged.
• Resting plasma contains free t-PA (10-60 IU/L) and free U-PA (50-100 IU/L).
• No significant difference in t-PA or U-PA response was observed between DVT and non-DVT groups during venous occlusion.

Conclusions:

• The developed bioimmunoassays offer sensitive and quantitative measurement of t-PA and U-PA, overcoming limitations of previous methods.
• Exercise primarily impacts t-PA levels, influencing fibrinolysis, whereas U-PA is less affected.
• The findings challenge the notion that "non-responders" to t-PA are more susceptible to DVT, suggesting a need to re-examine this hypothesis.