Histochemical demonstration of 5-hydroxytryptamine in platelets and megakaryocytes

A histochemical fluorescence method for the demonstration of biogenicmonoamines was applied to the smear preparation of peripheral blood plateletsand bone marrow megakaryocytes of rabbits and humans. The fluorescenceobtained was identified as 5-HT by histochemical and pharmacologic criteria.With this technic, the following results were obtained: (1) A large amountof 5-HT was present in platelets and in mature platelet-forming megakaryocytes. (2) Only a small amount of 5-HT was demonstrable in the intermediate maturation forms of megakaryocytes with lack of platelet budding.

The possibility that the 5-HT detected was derived from (a) transport of5-HT formed elsewhere, and/or (b) 5-HT formation from 5-HTP in themegakaryocytes themselves during their maturation was discussed.

Submitted on October 24, 1966 Accepted on February 20, 1967