Pergamon ThmmbesisReseamh,Vo L 87, N0. 4, pp.405-410,1997 %~~t~ E97ElsevierSdcmeIJd PrintedintheUSA. ~li@tSIES~@ 0049-3848197$17.00 + .00 PII S0049-3848(97)00144-8 DIFFERENTIALEFFECTOFALOW-MOLECULAR-WEIGHT HEPARIN (.DALTEPARIN) ANDUNFIL4CTIONATEDHEPARINONPLATELET INTERACTIONWITHTHESUBENDOTHELIUMUNDERFLOW CONDITIONS A. Serra,J. Esteve,J.C. Reverter,M. Lozano,G. Escolarand A. Ordinas. Departmentof Hemotherapyand Hemostasis.HospitalClinic.Barcelona.Spain (Received13Februaiy1997byEditorJ. Aznar;reviseo7accepted29 June 1997) Abstract Efkcts of heparins on platelet flmctionare controvemial,but perfitsionstudies, that simulatephysiological conditions, mighthelpto explaintheirclinicalbehaviour.We used a perfkion systemto test the effectunfkwtionatedheparinand a low-molecular-weight heparin (dalteparin,FragminR)on plateletadhesionpromotedby a damaged vascular surface.Normal blood samplescontainingincreasingconcentrationsof unfkctionated hepminanddalteparinwereperfhsedthroughannularchamberscontainingenzyrnatically denuded rabbit aorta segments (5 min at 800 see-’). Segments were evaluated morphometicailymeasuringthetotalsurfacecoveredbyplateletsandby largeaggregates (thrombi).Unflactionatedheparininhibitedplateletinteractionwithsubendothelium in a lesser extentthan dalteparinin both coveredsurfaceand thrombi(@O.01).At heparin dosesthat causedmaximalinhibition coveredsurfhcewas 10.OYO *3.lYowith dalteparin and 18.3°A*4.2’%0 withunfractionatedheparin,andthrombiwere5.6Y0+3.2’%0 and 12.3°A +3.0%,respectively. Theseresultsmay collaborateto explainsomedifferencesobserved intheclinicalresultsobtainedwith unfractionated heparinand withdalteparin. 0 1997ELsevier ScienceLid Low-molecular-weight heparins(LMWHS),that are flagmentsof unfmctionatedheparin (UFH) producedby either chemical or enzymaticdepolymerizatiowhave been introducedin clinical practice during late years with good antithromboticresults and a lower rate of bleeding complicationsthan UFH (1,2,3).Both LMWH and UFH bind antithrombinIII to enhanee their effects inhibitingblood coagulationf-rs, but LMWH and UFH have several functional Key words: untlactionatedheparinj low-molecular-weight heparin, dalteparimplatelet fimction, plateletadhesion,flowingsystems. Correspondingauthor:Dra.AngelicaSe- DepartmentofHemotherapyand Hemostasis,Hospital Clinic,Villarroel170,08036Bareelow Spain.Phone:(34 3) 2275400 ext 2087.Fax: (343) 227 5448. 405