Disaggregation of Platelet Aggregates Formed by the Action of Thrombin in the Presence of Hydrogen Peroxide

E. N. Loiko^1*, A. B. Samal¹, and V. I. Lapsha²

¹Department of Biochemistry, Belarusian State University, pr. F. Skoriny 4, Minsk 220050, Belarus; fax: (017) 209-5445; E-mail: Loiko@bsu.by

²Institute of Physiology, Belarusian National Academy of Sciences, ul. Akademicheskaya 28, Minsk 220072, Belarus

^* To whom correspondence should be addressed.

Received July 14, 2003; Revision received August 1, 2003

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The aggregation and change in the intracellular Ca²⁺ concentration induced by thrombin (0.005-0.22 U/ml) in the presence of H₂O₂ (0.05-0.6 mM) was investigated. Under the chosen experimental conditions (incubation time of platelets with H₂O₂ not more than 15 sec), H₂O₂ neither accelerated nor inhibited the thrombin-induced platelet aggregation. However, platelet aggregates formed by the action of thrombin in the presence of H₂O₂ were unstable and disaggregated. Disaggregation was abolished by catalase added after thrombin. The disaggregation effect was dose-dependent; the process of disaggregation was confirmed by electron microscopy. Hydrogen peroxide did not influence thrombin-induced increase in the intracellular Ca²⁺ concentration, but dose-dependently accelerated Ca²⁺ extrusion from the platelet cytoplasm.

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KEY WORDS: hydrogen peroxide, platelet disaggregation, thrombin, Quin 2, intracellular Ca²⁺

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