Effects of ADP and ATP on bovine fibrinogen- and ristocetin-induced platelet aggregation in Glanzmann's thrombasthenia.

With thrombasthenic platelets, aggregation induced by ristocetin (R) and bovine fibrinogen (BF) is reversible, provided ATP is not added to the system. ADP inhibits BF and R induced aggregation, and when added after the onset of aggregation causes rapid disaggregation. ATP prevents these inhibitory and disaggregation effects of ADP. A mechanism is suggested whereby co-operative effects occur between receptors in the membranes of thrombasthenic platelets.