Fig. 4.

Inhibition of ADP-induced, P2Y₁-mediated platelet Ca²⁺ increase by diadenosine 5′,5‴-P¹,P⁴-tetraphosphate (Ap₄A) analogs. The increase in platelet cytosolic Ca²⁺ in response to 3 μM ADP, with and without addition of Ap₄A analogs, was measured by whole blood flow cytometry with the Ca²⁺ indicator FLUO-4. The percentage inhibition was calculated relative to ADP + vehicle (0% inhibition) and vehicle alone (100% inhibition). The results shown are mean ± standard error of the mean. Data are from three or four independent experiments. Compounds: 1, diadenosine 5′,5‴-P¹,P⁴-dithiotetraphosphate; 2, diadenosine 5′,5‴-P²,P^3-chloromethylenetetraphosphate; 3, diadenosine-5′,5‴-P¹-thio-P²,P³-chloromethylenetetraphosphate; 4, diadenosine-5′,5‴-P¹,P⁴-dithio-P²,P³-chloromethylenetetraphosphate.