Adrenaline potentiates PI 3-kinase in platelets stimulated with thrombin and SFRLLN: role of secreted ADP

Adrenaline significantly potentiated late thrombin- and SFRLLN-induced PtdI ns(3,4)P-2 production. Furthermore, the potentiating effect of adrenaline o n thrombin-induced PtdIns(3,4)P-2 production was independent on secreted AD P, whereas, the effect of adrenaline on SFRLLN-induced PtdIns(3,4)P-2 produ ction was completely dependent of secreted ADP, However, the ADP-dependent accumulation of PtdIns(3,4)P-2 was not required for irreversible platelet a ggregation induced by SFRLLN in the presence of adrenaline. It is concluded that adrenaline can replace secreted ADP to potentiate PtdIns(3,4)P-2 prod uction in thrombin-stimulated but not in SFRLLN-stimulated platelets, thus demonstrating a qualitative difference between platelet stimulation by thro mbin and the thrombin receptor activating peptide SFRLLN. (C) 2000 Federati on of European Biochemical Societies, Published by Elsevier Science B.V. Al l rights reserved.