[Serotonin metabolism in the tissue of glial brain tumors].

Content of serotonin was distinctly decreased in human brain glial tumors and in transplanted rat gliomas. Activities of 5-hydroxytryptophane decarboxylase and mitochondrial monoamine oxidase were also lowered as compared with the normal state. Content of tryptophane (the main precursor of serotonin) was increased in human and animal tumor tissues; 5-hydroytryptophane was not found in gliomas. A decrease in the tryptophane hydroxylase activity occurred apparently in glioma tissues. The decrease in activity of 5-hydroxytryptorphane decarboxylase, found in tissues of brain glial tumors, might be considered as an adaptive mechanism, since content of serotonin was increased in the tumor tissues after administration of exogenous 5-hydroxytryptophane.