11564
Tissue IDO was investigated using quantitative RT - PCR and Western blot , whereas tryptophan , kynurenine , and 5 - hydroxytryptamine ( 5 - HT ) concentrations were quantified by HPLC and ELISA .
 Chemical: tryptophan; Chemical: kynurenine; Chemical: 5 - hydroxytryptamine; Chemical: 5 - HT
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: tryptophan; Chemical: kynurenine; Chemical: 5 - hydroxytryptamine; Chemical: 5 - HT