title: [Effect of unfractionated and low-molecular-weight heparin on platelet aggregation and in vitro bleeding time in dogs].
abstract: The aim of the present study was to examine the influence of unfractionated heparin (UFH) and low molecular weight heparin (LMWH) on the function of canine thrombocytes. This was performed by adding different concentrations of UFH or LMWH to platelet rich plasma (PRP) or blood of healthy dogs: 0.2, 0.5, 1, 2, 5, 10, 20, and 50 I.U./ml UFH or Anti-FXaU/ml LMWH, respectively (aggregation induced by thrombin additionally: 0.025, 0.05, and 0.1 I.U./ml UFH or Anti-FXaU/ml LMWH.) Platelet aggregation induced by ADP, collagen or thrombin with the BORN method (n = 11) as well as the in vitro bleeding time using the analyzer PFA-100 (n = 5) were examined. Additionally, a specific test assay for ADP induced platelet aggregation was performed which enabled an individual adjustment of the aggregation maximum at 30-40% in the control measurements (n = 6). The most prominent effect was noted in the platelet aggregation induced by thrombin. The aggregation maximum of the platelet aggregation induced by 1 I.U./ml thrombin (final concentration) was significantly lower in all of the testet UFH concentrations > or = 0.025 I.U./ml UFH in comparison to control measurements. If the aggregation was induced by 10 I.U./ml thrombin a significant reduction of the aggregation maximum was restricted to UFH concentrations > or = 0.5 I.U./ml. The addition of LMWH to canine PRP resulted in a distinct decrease (p < 0.01) of the maximum aggregation induced by 1 I.U./ml thrombin in concentrations > or = 0.2 Anti-FXaU/ml LMWH. A slight decrease of the maximum aggregation induced by collagen was only found for UFH at activities > or = 20 I.U./ml. No significant systematic influence could be demonstrated for LMWH on the aggregation induced by collagen as well as for LMWH and UFH on the platelet aggregation induced by ADP. Capillary in vitro bleeding time (closure time) was prolonged only after adding high concentrations of UFH (> or = 10 I.U./ml) and LMWH (> or = 50 Anti-FXaU/ml) to the sample material. The results document the unimportant influence of therapeutic levels of UFH and LMWH on platelet function in dogs. Therefore, the remarkable inhibition of the aggregation induced by thrombin reflects mainly the antithrombin effect.
authors.affiliation: Klinik für kleine Haustiere, Tierärztlichen Hochschule Hannover.
authors.forename: K
authors.initials: K
authors.lastname: Nimmerfall
authors.forename: R
authors.initials: R
authors.lastname: Mischke
mesh_terms: D000818:Animals; D001760:Bleeding Time / Q000379:methods / Q000662:veterinary*; D004285:Dogs; D006493:Heparin / Q000494:pharmacology*; D006495:Heparin, Low-Molecular-Weight / Q000494:pharmacology*; D066298:In Vitro Techniques; D010974:Platelet Aggregation / Q000187:drug effects*; D012016:Reference Values
chemical_list: D006495:Heparin, Low-Molecular-Weight; D006493:Heparin
vernacular_title: Einfluss von unfraktioniertem und niedermolekularem Heparin auf die Thrombozytenaggregation und die In-vitro-Blutungszeit beim Hund.