Platelet 5-hydroxy-tryptamine in thrombotic and non-thrombotic diseases

It is generally accepted that platelets from the main constituent of a thrombus. Experimental work has shown that 5-hydroxy-tryptamine (5 HT) in a concentration of 0.06 mg/ml produces clumping of the platelets. In view of this it was decided to estimate platelet 5 HT in thrombotic and non-thrombotic diseases. Thirty-five patients were investigated. Estimations of 5 HT were made on washed platelets rather than platelet-rich plasma which has been used in previous studies. Three groups were recognized on the basis of platelet 5 HT values. The first group consisted of five subjects who were clinically asymptomatic at the time of investigation but died 24 to 48 hours later and were shown at autopsy to have deep-vein thrombosis and pulmonary embolism; they had the highest level of platelet 5 HT. The second group comprised eight patients with cerebral thrombosis whose platelet 5 HT ranged between 1529 and 2183 ng/10-9. There were 22 subjects in the third group (11 apparently normal and 11 with different pathologies). Their platelet 5 HT ranged from 611 to 877 ng/10-9 and did not vary in the different pathological conditions studied. Since the highest level of platelet 5 HT was observed in patients prior to the formation or embolization of a thrombus, it is suggested that this may have some role in initiating thrombus formation.