Platelet serotonergic mechanisms in patients with cancer of the urinary bladder.

Platelet reactivity of hypertensive patients and patients with cancer of the urinary bladder was examined in vitro in comparison with normotensive patients. A significant increase in free serotonin in the plasma of patients with cancer of the bladder and a less pronounced increase in hypertensive subjects was observed. The platelets in neoplastic disease and hypertension showed a significant reduction in the kinetics of serotonin uptake. However, the release reaction was markedly higher, compared with healthy volunteers. Enhancement of platelet aggregation with serotonin was much greater in patients with cancer of the bladder than in control groups and in hypertensive patients. These data indicate increased sensitivity to serotonin within the platelets of patients with cancer of the urinary bladder.