Dipyridamole affects myocardial adenosine kinase activity.

Adenosine kinase (EN 2.7.1.20) from rat and dog heart was purified until it was devoid of adenosine deaminase activity. A stimulation of adenosine kinase activity by dipyridamole was observed when the enzyme was assayed under optimal conditions. At low substrate concentrations adenosine kinase was inhibited by the drug. It increased the Km for adenosine sevenfold. The effects of dipyridamole were Mg2+-dependent. The adenosine-sparing action of dipyridamole at low substrate concentrations is in keeping with the vasodilatory action of the drug.