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Calin from Hirudo medicinalis, an inhibitor of platelet adhesion to
collagen, prevents platelet-rich thrombosis in hamsters
H Deckmyn, JM Stassen, I Vreys, E Van Houtte, RT Sawyer and J Vermylen
Center for Molecular and Vascular Biology, University of Leuven, Belgium.
Interaction between exposed collagen and platelets and/or von Willebrand
factor is believed to be one of the initiating events for thrombus
formation at sites of damaged endothelium. Interference with this mechanism
may provide an anti-thrombotic potential. Calin, a product from the saliva
of the leech Hirudo medicinalis, was tested in vitro and for its in vivo
activity in a thrombosis model in hamsters. Calin specifically and dose
dependently (IC50:6.5 to 13 micrograms/mL) inhibited human platelet
aggregation induced by collagen. In addition, specific platelet adhesion
onto microtiter wells coated with collagen and detected with a monoclonal
antiglycoprotein IIb/IIIa antibody- conjugated with horseradish peroxidase,
could be completely prevented with Calin (IC50:22 micrograms/mL). A
dose-response curve was constructed in groups of six hamsters in whom a
standardized trauma was induced on the femoral vein. Thrombus formation was
followed continuously using video recording and processing of the image
obtained upon transillumination of the vessel. Intravenous Calin dose-
dependently inhibited platelet-rich thrombus formation in this model with
an ED50 of 0.07 mg/kg and complete inhibition with 0.2 mg/kg. No effects
were seen on coagulation tests or bleeding times, whereas ex vivo
aggregation induced by collagen was inhibited dose dependently. Local
application of leech saliva, Calin, hirudin, or the combination of the
latter two into the bleeding time wound of hamsters resulted in a mild
prolongation of the bleeding time (twofold to threefold). A similar
experiment in baboons did not cause any prolongation of the bleeding time.
This is in sharp contrast with the long-lasting bleeding after a leech bite
itself in both species. Calin from the leech Hirudo medicinalis is able, by
binding to collagen, to effectively interfere with platelet-collagen
interaction, which results in an antithrombotic effect observed in a
platelet-rich thrombosis model in hamsters.
Volume 85,
Issue 3,
pp. 712-719,
02/01/1995
Copyright © 1995 by The American Society of Hematology
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