Some properties of adenosine deaminase from vascular smooth muscle and its inhibition by various vasodilators

Because of some uncertainties still existing about the role of adenosine deaminase in the drug-influenced adenosine breakdown, the authors isolated this enzyme from vascular smooth muscle and studied the inhibition of its activity by some vasodilating drugs. The adenosine deaminase was purified 360-fold from bovine carotid artery by means of (NH4)2SO4-precipitation, heat treatment, and gel filtration. This enzyme behaves in a similar way as preparations of the same enzyme from other tissues in respect to pH-dependence and Michaelis constant. The vascular enzyme is inhibited by dipyridamole and trapymine in a competitive manner, hexobendine and lidoflazine are without any effect. The results lead to the conclusion that the inhibition of vascular adenosine deaminase does not constitute the sole cause of the adenosine-potentiating effect of the vasodilating drugs studied.