Ionophore a 23187: some effects on platelet aggregation and clot retraction.

The ionophore for divalent cations, A 23187, induces plate aggregation and clot retraction. Acetylsalicyclic acid has a potentiating effect on the aggregation induced by A 23187 in platelet-rich plasma, while it inhibits the aggregation of washed platelets. Acetylation of plasma proteins could be the reason of the increased platelet aggregation induced by A 23187 in the presence of acetylsalicyclic acid. Platelet aggregation by A 23187 is probably activated by the passage of Ca2+ through the platelet membrane(s); the aggation, clot retraction by A 23187 requires increased availability in the intracellular space of both Ca2+ and Mg2+.