Cambridge H, Lees P, Hooke R E, Russell C S
Department of Veterinary Basic Sciences, Royal Veterinary College, North Mymms, Hatfield, UK.
Equine Vet J. 1991 Mar;23(2):123-7. doi: 10.1111/j.2042-3306.1991.tb02736.x.
The antithrombotic effects of aspirin at two dose rates (4 mg/kg and 11 mg/kg bodyweight [bwt] were evaluated in normal, healthy ponies by measuring template bleeding time. Inhibition of platelet aggregation in response to adenosine diphosphate (ADP) and collagen was evaluated and cyclo-oxygenase activity was monitored by radioimmunoassay of thromboxane B2 (TXB2), the stable metabolite of thromboxane A2 (TXA2). TXB2 was measured in serum and platelet rich plasma. Bleeding time was prolonged significantly until 48 h after treatment at 12 mg/kg bwt and until 4 h at the lower dose rate. Synthesis of TXB2 and collagen induced aggregation were diminished for much greater periods with similar results at each of the dose rates. The prolonged effects of aspirin on platelet function occurred in spite of a very short plasma half-life of aspirin, because of its irreversible action on platelet cyclo-oxygenase. The results show that low dose aspirin has a potential role in antithrombotic therapy in horses although the relationship between skin bleeding time in normal horses and improvement of clinical conditions requires further research and evaluation in clinical trials. TXB2 measurement appears to overestimate the duration of antithrombotic effects of aspirin in vivo.
通过测量模板出血时间，在正常、健康的小马中评估了两种剂量率（4毫克/千克和11毫克/千克体重[bwt]）的阿司匹林的抗血栓形成作用。评估了对二磷酸腺苷（ADP）和胶原蛋白反应的血小板聚集抑制情况，并通过血栓素B2（TXB2）的放射免疫测定法监测环氧化酶活性，TXB2是血栓素A2（TXA2）的稳定代谢产物。在血清和富含血小板的血浆中测量TXB2。在12毫克/千克体重的剂量下，出血时间显著延长至治疗后48小时，在较低剂量率下延长至4小时。TXB2的合成和胶原蛋白诱导的聚集在更长的时间内减少，在每个剂量率下结果相似。尽管阿司匹林的血浆半衰期非常短，但由于其对血小板环氧化酶的不可逆作用，阿司匹林对血小板功能仍有延长的作用。结果表明，低剂量阿司匹林在马匹抗血栓治疗中具有潜在作用，尽管正常马匹的皮肤出血时间与临床状况改善之间的关系需要在临床试验中进一步研究和评估。TXB2测量似乎高估了阿司匹林在体内的抗血栓作用持续时间。
