Figure 2.

Influence of ticlopidine on recombinant human NTPDase activities. Enzymatic assays were carried out with lysates from COS-7 cells transfected with an expression vector encoding the indicated enzyme. The substrate (ATP or ADP at the concentration of 100 μM) was added alone or together with ticlopidine at the concentration of either 100 μM or 1 mM. The 100% activity in the absence of ticlopidine corresponded to the following: for human NTPDase1 to 670 ± 29 and 550 ± 21 nmol P_i·min⁻¹ ·mgprotein⁻¹ for ATP and ADP as substrates, respectively (a), for human NTPDase2 to 1023 ± 58 nmol P_i· min⁻¹·mgprotein⁻¹ for ATP as substrate (b), for human NTPDase3 to 256 ± 37 and 103 ± 10 nmol P_i·min⁻¹·mgprotein⁻¹ for ATP and ADP as substrates, respectively (c), and for human NTPDase8 to 148 ± 16 and 33 ± 6 nmol P_i·min⁻¹·mgprotein⁻¹ for ATP and ADP as substrates, respectively (d). Data are presented as the mean ± SD of 3 experiments carried out in triplicate. *P = 0.018; **P = 0.0002.