Cloricromene inhibits the activation of human platelets by ADP alone or in combination with adrenaline

Cloricromene may inhibit platelet activation induced by several agonists. In this study we report that ADP and adrenaline synergistically promote platelet aggregation and cytoplasmic Ca2+ movements in aequorin-loaded platelets. Cloricromene caused dose-dependent reduction in platelet aggregation and cytoplasmic Ca2+ movements after exposure of the cells to a low concentration of ADP (2 microM) or to a combination of ADP (2 microM) and adrenaline (10 microM). Cloricromene's inhibitory action may be of considerable pharmacological interest since platelet activation by a combination of agonists may mimic the conditions under which thrombosis occurs in vivo.