Platelet aggregation by thimerosal: role of ADP and SH groups

Area of Science:

• Biochemistry
• Hematology
• Pharmacology

Background:

• Thimerosal is a known sulphydryl inhibitor.
• Platelet aggregation is a critical hemostatic process.
• Understanding the mechanisms of platelet aggregation is crucial for diagnosing and treating bleeding disorders.

Purpose of the Study:

• To investigate the mechanism by which thimerosal induces platelet aggregation.
• To determine the role of sulfhydryl groups in thimerosal-induced platelet aggregation.
• To explore the involvement of other factors like ADP, fibrinogen, and ions in this process.

Main Methods:

• Platelet rich plasma aggregation assays were performed using varying concentrations of thimerosal.
• The effect of thimerosal on platelet aggregation was assessed in the presence and absence of specific inhibitors and cofactors.
• Aggregation studies were conducted in patients with specific platelet function defects.

Main Results:

• Thimerosal induced platelet aggregation across a broad concentration range.
• Low doses resulted in a monophasic response with a lag phase; high doses caused an immediate biphasic response.
• Aggregation was mediated by thimerosal's binding to sulfhydryl groups and was independent of ADP, fibrinogen, von Willebrand factor, calcium, and magnesium ions.
• Thimerosal-induced aggregation was normal in thrombocytopathia but impaired in Glanzmann's thrombasthenia.
• Mercaptopropionglycine inhibited thimerosal-induced aggregation, suggesting the importance of sulfhydryl groups.

Conclusions:

• Thimerosal induces platelet aggregation through direct interaction with sulfhydryl groups.
• The mechanism is distinct from ADP-mediated aggregation and is not influenced by common platelet agonists or cofactors.
• Sulfhydryl groups play a significant role not only in thimerosal-induced aggregation but potentially in aggregation induced by thrombin, collagen, and ADP as well.