Low-density lipoprotein amplifies the platelet response to serotonin in human plasma.

The effect of low-density lipoprotein, serotonin and low-density lipoprotein plus serotonin on platelet aggregation (measured ex vivo in plasma) was studied in 28 normotensive subjects (15 non-smokers, 13 smokers) and 15 previously untreated non-smoking patients with essential hypertension. Low-density lipoprotein alone had no platelet-activating effect. Serotonin-induced platelet aggregation was enhanced by low-density lipoprotein in both the normotensive and the hypertensive subjects. The platelet response to low-density lipoprotein plus serotonin was higher in the smokers than in the non-smokers; it was also higher in the hypertensive patients than in the normotensive controls. We conclude that low-density lipoprotein activates platelets in plasma via an interaction with a serotonergic mechanism. Low-density lipoprotein amplifies the serotonin-induced platelet aggregation (normally reversible), making it irreversible. A higher platelet response to low-density lipoprotein plus serotonin in patients with essential hypertension may be of pathophysiological relevance in respect to the thrombovascular lesions accompanying hypertension and/or atherosclerosis.