Relationships between serum lipids, serotonin, platelet aggregation and some fibrinolytic parameters in humans.

We have studied relationships between serum lipids, plasma serotonin (5-hydroxytryptamine, 5-HT), platelet aggregation in the platelet-rich plasma (PRP), and some fibrinolytic parameters in healthy volunteers. LDL was positively related to 5-HT-induced platelet aggregation. Higher serum HDL levels were related to higher fibrinolytic activity expressed by shorter euglobulin clot lysis time (ECLT). No correlation existed between serum lipids and plasma 5-HT. Plasma 5-HT was found to be related to tissue plasminogen activator (t-PA), suggesting some link between plasma serotonin and the release of t-PA from endothelial cells. There were mutual relations among fibrinolytic parameters such as tissue plasminogen activator (t-PA) antigens, total plasminogen activator inhibitor-1 (PAI-1), t-PA-PAI-1 complex, free PAI-1, and ECLT. In conclusion higher LDL may be more thrombogenic due to enhanced 5-HT induced platelet aggregation whereas high HDL may be more protective against thrombosis due to enhancement of fibrinolysis.