Thromb Haemost 1995; 74(04): 1163-1168
DOI: 10.1055/s-0038-1649897
Original Article
Schattauer GmbH Stuttgart

Effects of Heparin and Hirudin on Thrombin Generation and Platelet Aggregation after Intrinsic Activation of Platelet Rich Plasma

Siegfried Gallistl
The Department of Pediatrics, University of Graz, Austria
,
Wolfgang Muntean
The Department of Pediatrics, University of Graz, Austria
,
Hans Jörg Leis
The Department of Pediatrics, University of Graz, Austria
› Author Affiliations
Further Information

Publication History

Received 28 March 1995

Accepted after resubmission 05 July 1995

Publication Date:
09 July 2018 (online)

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Summary

The effects of unfractionated heparin (UH) and recombinant hirudin (rH) on prothrombin activation, free thrombin generation, and platelet aggregation induced by endogenously generated thrombin after intrinsic activation of platelet rich plasma were compared. Free thrombin generation and platelet aggregation were assessed simultaneously by delaying fibrinogen polymerisation with GPRP.

UH more effectively inhibited prothrombin activation and free thrombin generation than rH. Increasing concentrations of rH had hardly any effect on the peak amount of free thrombin, while in the presence of 400 nM UH only traces of free thrombin were detected. Comparison of TAT and THC (thrombin-hirudin complex) generated until the onset of platelet aggregation on a molar basis showed that much more thrombin was inactivated in the presence of rH than in plasma containing UH. The explosive generation of free thrombin in hirudinized plasmas was accompanied by a markedly steeper aggregation curve as compared to heparinized plasmas. The generation of thromboxane B2 was markedly delayed in the presence of UH but not influenced in the presence of rH.

Our results suggest that UH is more effective than rH in inhibiting prothrombin activation after intrinsic activation of platelet rich plasma, while rH prevents clotting more by direct inactivation of already generated thrombin. The inability of even high concentrations of rH to prevent the explosive generation of free thrombin might contribute to the observed inefficiency of rH to inhibit platelet aggregation.