Pharmacological action of 5'-methylthioadenosine on isolated rabbit aorta strips

The effects of 5'-methylthioadenosine (MTA) and adenosine analogues on isolated rabbit thoracic aorta strips were studied in vitro. High concentrations (500-1,000 microM) of adenosine analogues produced dose-dependent relaxation in isolated rabbit thoracic aorta strips. The relative potencies of relaxant effect were MTA greater than N6-phenylisopropyladenosine greater than 2-chloroadenosine on a molar basis. MTA (50-1,000 microM) suppressed the contraction induced by norepinephrine in isolated rabbit thoracic aorta strips in a concentration-dependent manner. Nucleoside uptake inhibitor dipyridamole did not impair the MTA actions. Pretreatment of the aorta strips with theophylline, an adenosine receptor antagonist, blocked the actions of MTA. MTA showed a relaxant effect in KCl-contracted aorta suggesting that MTA did not affect the metabolism or reuptake of norepinephrine. The present experiments suggest that MTA has a pharmacological action on the arterial smooth muscle cells mediated through adenosine receptors.