Variations of peripheral markers of serotoninergic system in selected vascular patients

Serotonin (5-HT), a decarboxylated derivative of tryptophan, is synthesized in the enterochromaffin cells and released into blood stream to be incorporated into platelets. At the site of endothelial lesions, platelets aggregate and secrete 5-HT that presents several vascular actions involved in thrombosis and atherogenesis. In fact, 5-HT may induce vasoconstriction in the presence of endothelial injury, aggregation of platelets, and mitogenesis of arterial smooth muscle cells and endothelial cells. It may also contribute to the vascular inflammation associated with atherogenesis by increasing the synthesis of Interleukin-6 in vascular smooth muscle cells. We evaluated serotonin levels in plasma and platelets of patients with unstable angina and ischemic stroke, to identify an association between serotonin and atherosclerosis of coronary and cerebral arteries.

Twenty patients (14 men, 6 women, mean age 69 +/- 10 years) with unstable angina and 15 patients (7 men, 8 women, mean age 81 +/- 10 years) with ischemic stroke were included in the study. Twenty-four healthy subjects matched for age and sex constituted the control group. Blood samples were drawn in the morning to determine plasma and platelet concentrations of serotonin. In patients with unstable angina serotonin levels in platelets were significantly lower (p < 0.001) than those observed in controls, while serotonin concentrations in plasma did not significantly differ from those found in controls. In patients affected by stroke serotonin levels in plasma and in platelets did not significantly differ from those found in normal subjects.

Our findings may contribute to the knowledge to different mechanisms involved in the pathogenesis of cardiac and cerebral ischemia.