Ecto‐enzymes and metabolism of extracellular ATP

Extracellular ATP can produce various effects acting via P 2 ‐purinoceptors. ATP is rapidly broken down by ecto‐ATPase and other ecto‐enzymes that limit its effect. Further, adenosine, a metabolite of ATP breakdown, can produce its own effect acting via P 1 ‐purinoceptors, sometimes masking the effects of ATP. An inhibitor of ATP degradation would be a useful pharmacological tool to discriminate between effects of ATP and its metabolites, as well as to potentiate its actions. Diverse compounds that have been claimed to be inhibitors of ATP‐metabolising ectoenzymes are evaluated, but specific and selective Ca 2+ /Mg 2+ ‐dependent ecto‐ATPase inhibitors still appear to be lacking.