Analysis of the metabolites of [I-123]β-CIT in plasma of human and nonhuman primates

Andreas Heinz, Douglas W. Jones, Julia G. Gorey, Michael B. Knable, Kan Sam Lee, Richard C. Saunders, Daniel R. Weinberger

Research output: Contribution to journalArticle

Abstract

[I-123]β-CIT is a single photon emission computed tomography (SPECT) radioligand that has been used for in vivo studies of the dopamine and serotonin transporters. Two metabolite peaks of β-CIT have been observed by high performance liquid chromatography (HPLC), but neither has been chemically identified. One major metabolite is clearly hydrophilic. Previous reports have not agreed on the amount of the second metabolite and the extent to which it may cross the blood-brain barrier. To clarify this controversy, we have studied β-CIT metabolites using a protein precipitation method and an organic extraction method followed by HPLC separation. Plasma from both human and nonhuman (rhesus) primates was analyzed. Concentrations of the second metabolite were substantially lower in rhesus than in human for nearly equal parent concentrations. Furthermore, in rhesus the second metabolite is partially soluble in the organic solvent ethyl acetate, whereas in human it is essentially insoluble. These observations account for the contradictions in the literature. The hydrophilic nature of the human metabolite renders it unlikely that it crosses the blood-brain barrier in sufficient quantities to interfere with the quantitative assessment of dopamine transporter densities.

Original languageEnglish (US)
Pages (from-to)306-308
Number of pages3
JournalSynapse
Volume25
Issue number3
DOIs
StatePublished - Mar 1 1997
Externally publishedYes

Keywords

  • 2β-carbomethoxy-3β-(4-iodophenyl)tropane
  • 5-HT transporter
  • HPLC
  • SPET
  • dopamine transporter
  • metabolism
  • single photon emission computed tomography

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience

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