ENDOGENOUS SEROTONIN IN HUMAN BLOOD-PLATELETS - FACTORS THAT MAY INFLUENCE REFERENCE VALUES

The endogenous content of serotonin in human platelets has been used i n many clinical studies to indicate platelet activation. A decrease in platelet serotonin compared with controls has been regarded as an ind icator of platelet activation. However, the results published are diff icult to compare, because of huge variations in endogenous serotonin b etween control groups in different investigations, This is likely to b e because of lack of standardization. Several factors that influence t he endogenous platelet serotonin content were studied in more than 200 blood donors. The most important factor was the total g force of the centrifugation used to isolate platelets. Also the age and sex of plat elet donors, number of platelets in platelet-rich plasma, and mean pla telet volume influenced normal serotonin values, Using a standardized centrifugation procedure (2700g min) the mean endogenous serotonin was 2.80 nmol/10(9) platelets in young women and 2.58 in elderly women, a nd 2.67 in young men and 2.30 in elderly men, The differences both for age and sex were statistically significant, Endogenous platelet serot onin shows intrapersonal stability over time, since endogenous platele t serotonin did not change on repeated venepuncture for 9 weeks, Facto rs such as age, sex and isolation procedure must therefore be consider ed when endogenous platelet serotonin are studied in relation to disea se and treatment.