Effect of the ecto-ATPase inhibitor, ARL 67156, on the bovine chromaffin cell response to ATP

Bovine chromaffin cells contain an ecto-ATPase (K(m)=1.57 +/- 0.27 x 10(-4) M) which can hydrolyze ATP present in the culture media. ARL 67156 is a competitive inhibitor of this ATPase (K(i)=2.55 +/- 1.36 x 10(-7) M). A small increase in potency (threefold) is seen when ARL 67156 is included during measurement of ATP-stimulated inositol phosphate formation. ARL 67156 also acts on chromaffin cell P2Y receptors to increase inositol phosphate formation (EC(50)=4.9 x 10(-5) M). It is useful as an ecto-ATPase inhibitor in studies with bovine chromaffin cells since it exhibits a 300-fold selectivity for the ecto-ATPase versus the P2Y receptor.