The ratio of plasma to whole-blood serotonin may be a novel marker of atherosclerotic cardiovascular disease.

Because atherosclerotic vascular lesions stimulate platelets, the platelets release serotonin (5-hydroxytryptamine, aka 5-HT). We therefore measured 5-HT concentrations not only in platelet-poor plasma but also in whole blood as a means of assessing vascular lesions. The plasma concentration of 5-HT tended to increase with age, whereas that in whole blood decreases. Therefore the ratio of the plasma to the whole-blood concentration of 5-HT (P/WB) increases with age. This may be a result of the activation of platelets in older subjects with atherosclerotic vascular damage. Patients who underwent coronary angiography (CAG) were classified into 4 groups according to diagnosis: effort-induced angina pectoris (eAP), old myocardial infarction (OMI), vasospastic angina pectoris (VSAP), and unstable angina (uAP). The mean plasma 5-HT concentration was significantly (P <.01) greater in patients with eAP, uAP, OMI, and VSAP than in healthy controls, whereas the concentration in whole blood was lower in patients with eAP than in healthy controls. When the P/WB ratios were calculated, the mean levels in all disease groups were significantly higher than that in the healthy controls. These findings suggested that 5-HT is released into the plasma from the platelets and that the concentration in the platelets decreases in patients with atherosclerosis.