SERUM LEVELS OF 5-HYDROXYINDOLE DERIVATES AFTER ADMINISTRATION OF L-5-HYDROXYTRYPTOPHAN ETHYL-ESTER

  • 1 January 1976
    • journal article
    • research article
    • Vol. 15  (1) , 171-182
Abstract
Serum levels of 5-hydroxytryptophan ethyl ester, 5-hydroxytryptophan, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid (5-HTPE, 5-HTP, 5-HT and 5-HIAA, respectively), were measured after i.v. administration of L-5-HTPE in humans, premedicated with a peripheral decarboxylase inhibitor. Semi-automated methods for the estimation of the 5-hydroxyindole derivatives are described. Only serum levels of 5-HTP and 5-HIAA were increased, indicating that the ethyl ester is rapidly hydrolyzed and that the decarboxylation of 5-HTP is in part inhibited. The levels of 5-HTP increased during the infusion, but dropped rapidly when the i.v. administration was terminated. Serum levels of 5-HIAA remained constant for at least 6 h, although during the same period the levels of 5-HTP do change markedly. The persistently increased serum levels of 5-HIAA suggests, that this metabolite is formed from the 5-HT stored in peripheral or central tissue. Serum levels of 5-HIAA may be indicative of changes of 5-HT metabolism during drug treatment. Levels of 5-HTP may be used for estimation of the availability of the ethylester of 5-HTP.