New approaches to thrombolytic therapy.

Area of Science:

• Biochemistry
• Molecular Biology
• Thrombolysis Research

Background:

• Tissue-type plasminogen activator (t-PA) is a serine protease distinct from urokinase.
• t-PA activates plasminogen to plasmin via cleavage of a specific peptide bond.
• Fibrin significantly enhances t-PA's activation rate through increased plasminogen affinity.

Purpose of the Study:

• To investigate the kinetic properties of t-PA in plasminogen activation.
• To elucidate the mechanism underlying t-PA's fibrin-specific action.
• To compare the thrombolytic efficacy of t-PA with urokinase.

Main Methods:

• Purification of t-PA from a human melanoma cell line.
• Kinetic analysis of plasminogen activation by t-PA.
• Evaluation of thrombolytic properties in animal models and humans.

Main Results:

• t-PA activation of plasminogen follows Michaelis-Menten kinetics.
• Fibrin dramatically lowers the Michaelis constant for t-PA, promoting clot-specific activation.
• Purified t-PA demonstrates superior specific thrombolytic activity compared to urokinase, with minimal systemic effects.

Conclusions:

• The fibrin-binding property of t-PA explains its targeted action on thrombi.
• t-PA facilitates specific thrombolysis by confining plasminogen activation to the fibrin surface.
• t-PA offers a promising therapeutic agent for thrombolytic treatment due to its high specificity.