Background: In this article, we aimed to investigate the effects of antithrombotic agents, including acetyl salicylic acid (ASA), clopidogrel, and tirofiban on the acetylcholine (ACh)- induced dilation responses in rat thoracic aorta segments.

Methods: Twenty-eight Wistar albino male rats weighing between 250-300 g were included in the study. The rats were randomly divided into four groups: the ASA group (n=7), the clopidogrel group (n=7), the tirofiban group (n=7), and the control group (n=7). Intraperitoneal (IP) injection of ASA (1.5 mg/kg) or clopidogrel (1 mg/kg) was administered 12 hours before the experiment. In the tirofiban group, 150 μgr/kg tirofiban IP was given twice at one and 12 hours before the experiment. The rats in the control group did not receive any medication. After the rats were decapitated, the segments of the thoracic aorta were removed and suspended in an oxygenated Krebs solution in a tissue bath, and the dose dependency in the responses to the ACh-induced dilation in the aortic rings were studied.

Results: The dilation responses of the aortic rings to ACh in the lowest molar concentration (10-9) were found to be reduced in the ASA (94.3%±3.3) and clopidogrel (94.6%±3.1) groups when compared with the control group (86.7%±8.1) (p<0.05). The responses to higher concentrations of ACh were observed to be similar in all of the groups.

Conclusion: Acetyl salicylic acid and clopidogrel treatments resulted in a slight delay of endotheliummediated relaxation while tirofiban had no significant effect. These findings suggest that ASA and clopidogrel may have a limited effect on endothelium-mediated vasodilation.

Keywords : Acetylsalicylic acid; clopidogrel; endothelium; tirofiban