title: Drug metabolite heterogeneity in cultured single cells profiled by pico-trapping direct mass spectrometry.
abstract: OBJECTIVE
  We investigated the heterogeneity of tafluprost metabolism in primary human hepatocytes at a single-cell level by live single-cell mass spectrometry (MS).
  
  
  METHODS
  Picoliter volumes of cytoplasm were analyzed by nano-electrospray ionization MS in order to obtain single-cell metabolite profiles. The subcellular components of a single tafluprost-treated human hepatocyte were isolated and the single-cell metabolite profile was compared with those of traditional bulk hepatocyte analysis.
  
  
  RESULTS
  In the bulk hepatocyte analysis, liquid chromatography-MS showed the averaged metabolism of tafluprost to tafluprost acid (TA) and β-oxidized metabolites. However, live single-cell MS showed that tafluprost metabolism varied among individual cells. In addition, there was significant variation in the quantities of TA and a major metabolite, dinor-TA, among cells, whereas there was no significant variation in 7-ethoxycoumarin metabolism.
  
  
  CONCLUSIONS
  Thus, live single-cell MS successfully detected the heterogeneity of drug metabolism in individual living hepatocytes.
authors.affiliation: Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Fukano
authors.forename: Naohiro
authors.initials: N
authors.lastname: Tsuyama
authors.forename: Hajime
authors.initials: H
authors.lastname: Mizuno
authors.forename: Sachiko
authors.initials: S
authors.lastname: Date
authors.forename: Mikihisa
authors.initials: M
authors.lastname: Takano
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Masujima
mesh_terms: D002470:Cell Survival; D002478:Cells, Cultured; D003374:Coumarins / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D011460:Prostaglandins F / Q000378:metabolism*; D059010:Single-Cell Analysis / Q000379:methods*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D003374:Coumarins; D011460:Prostaglandins F; C485333:tafluprost; C017299:7-ethoxycoumarin