Effect of aspirin on the contractility of aortic rings in vitro from spontaneously hypertensive rats.

The effect of Acetylsalicylic acid (ASA) on the responsiveness of rat aortic smooth muscle was investigated by comparing the contractility of aortic rings from SHR and WKY rats in response to alpha-agonist, phenylephrine (PE). Cumulative dose response curves for PE were generated from aortic rings of SHR and WKY rats in the presence and absence of 0.2mM ASA. To investigate the involvement of endothelium on ASA mediated effects, active tension was recorded for denuded and non-denuded rings from SHR animals in response to KCl and PE. Denuded and non-denuded aortic rings from SHR animals in the presence of ASA produced significantly higher active tension than in the absence of ASA. The reactivity of aortic rings from WKY control animals was not altered significantly in the presence of ASA. These studies suggest that ASA can also modulate aortic contractility through other mechanism(s) in addition to its effect on the metabolites of arachidonic acid. Significance of these observations is discussed below.