Tissue plasminogen activator (abbreviated tPA or PLAT) is a serine protease normally found on the surface of endothelial cells of veins, capillaries, the pulmonary artery, heart, and uterus, and is secreted after vascular injury. It converts the proenzyme plasminogen to plasmin, a fibrinolytic enzyme. Plasminogen is synthesized as a single chain, which is cleaved by tPA into the two chain disulfide linked plasmin.

Function

This enzyme plays a role in cell migration and tissue remodeling. Increased enzymatic activity causes hyperfibrinolysis, which manifests as excessive bleeding; decreased activity leads to hypofibrinolysis which can result in thrombosis or embolism.

Fibrinolysis (simplified). Blue arrows denote stimulation, and red arrows inhibition.

Gene

Alternative splicing of the tPA gene, tPA, produces three transcripts.

Clinical applications

Recombinant tPA is used in diseases that feature blood clots, such as pulmonary embolism, myocardial infarction and stroke. To be effective, tPA must be administered within the first three hours of the event to be given intravenously, or within six hours to be administered through an arterial catheter directly to the site of occlusion. The guideline in Ontario, Canada hospitals for ischemic strokes is that tPA must be given within 3 hours of the onset of symptoms. Because of this, only about 3% of patients qualify for this treatment. tPA appears to show benefit not only for large artery occlusions but also for lacunar strokes. Since tPA dissolves blood clots, there is risk of hemorrhage with its use.

Recently tPA has been used to dissolve thrombi associated with ischemic strokes and brain injury.

In addition, people with frostbite that were treated with tPA had fewer amputations than those that were not^[1].

Further reading

References

See also

• Thrombolysis
• Ultrasound-Enhanced Systemic Thrombolysis

External links

• http://www.americanheart.org/presenter.jhtml?identifier=4751
• Widening the Window : Strategies to buy time in treating ischemic stroke - Scientific American Magazine (August 2005)

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