Acetyisalicylic Acid (ASA) does not Prolong Bleeding Time in Rats
We have recently suggested (Thrombos. Diathes. haemorrh., 32, 242, 1974; Thrombos. Res., 1975, in press) that the role of platelets in the primary haeomostasis of rats may be questioned. Further evidence to this hypothesis is given by this study. Indeed, we have observed that ASA does not prolong the bleeding time in rats, whereas it inhibits in vitro collagen- or Thrombofax-induced aggregation of platelets obtained from the same animals after administration of the drug. Conscious Charles River rats, weighing 350 g., were used. Aspirin (Bayer) or lysine-acetylsalicylate (Flectadol, Maggioni) were given either per os or intrapertioneally at a dose of 200 mg/kg b.w. The effect on the bleeding time was measured 1 hour after the administration of the drug by 2 different techniques: either transecting the tip of the tails of paired animals or making 2 incisions on the tail of the same animal by an automatic, standardized template-like device (kindly provided by Prof. C. Praga, Milano). Preliminary experiments in control animals had shown no difference between the first and the second incision. The results are reported in the table.As can be seen, ASA not only did not prolong bleeding time, but markedly shortened it. The latter result was unexpected and we have no satisfactory explanation for ist.(Supported by Grant N. 73.00400.04 of the Italian Research Council (C. N. R.).)