Serotonin Levels in Platelet-Poor Plasma and Whole Blood from Healthy Subjects: Relationship with Lipid Markers and Coronary Heart Disease Risk Score

AIM: The serotonin level in platelet-poor plasma (PPP) is an important clinical marker for monitoring platelet activation accompanying vascular endothelial injury. We previously developed an HPLC method that combines column-switching with a post-column reaction to measure serotonin in PPP. This study determined serotonin levels in healthy volunteers and evaluated the possible relationship of serotonin levels with lipid markers and Framingham 10-year risk scores (FRS) for coronary heart disease. METHODS: Serotonin was isolated from samples using our HPLC method and converted into a fluorescent derivative with benzylamine for specific and sensitive detection. Lipid fractionation was also performed by HPLC. FRS was calculated using the following: age, sex, LDL cholesterol, HDL cholesterol, blood pressure, and smoking and diabetes status. RESULTS: The PPP serotonin to whole blood serotonin ratio (PPP/WB) and the PPP serotonin level correlated significantly with HDL cholesterol levels: r= 0.187, p< 0.05 and r= 0.184, p< 0.05, respectively. The PPP/WB ratio also correlated significantly with FRS (r= 0.176, p< 0.05). The reference range (95% confidence interval) of PPP and WB serotonin levels in healthy subjects were 0.86-16.96 and 385-1319 nmol/L, respectively. CONCLUSIONS: Significant positive correlations between the serotonin PPP/WB ratio and FRS suggest that the PPP/WB ratio can serve as a biomarker for estimating atherosclerotic cardiovascular risk.