Platelet interactions with a-thrombin and serotonin

The aim of the first part of this thesis was to study platelets from people with essential thrombocytosis. Platelets from ET patients present several abnormalities. We focused on the abnormalities related with serotonin, in particular we wanted : 1) to determine the sub-cellular distribution of the neurotransmitter 2) to evaluate 5-HT transport in platelets either untreated or pre-incubated with reserpine, a known inhibitor of serotonin transport inside the dense granules 3) to establish whether the decreased accumulation of serotonin in pathological platelets was due to a decreased number of dense granules 4) to investigate the efficiency of the dense granules to accumulate basic amines; 5) to determine the amounts of ATP and Ca2+ contained in the dense granules 6) to evaluate the role of tyrosine kinases in the tranport of serotonin in platelets of MPDs subjects. 7) to analyze the serotonin-induced platelet activation (cytosolic [Ca2+] increase). The second part of this thesis performed at the Scripps Research Institute (La Jolla, CA) in the laboratory directed by prof. Z.M. Ruggeri was to precisely define the functional role of tyrosine sulfation in the a-thrombin binding to GpIba, a receptor present in platelets, that play a pivotal role in haemostasis and thrombosis.