title: Protein precipitation: an expedient procedure for the routine analysis of the plasma metabolites of [123I]IBZM.
abstract: Plasma metabolite analysis of the single photon emission computed tomography (SPECT) D2/D3 receptor radiotracer (S)(-)-N-[(1-ethyl-2-pyrrolidinyl)methyl]-2-hydroxy-3-[123I]iodo-6-metho xybenzamide ([123I]IBZM) is needed for the equilibrium analysis of the SPECT data, in brain imaging studies involving bolus plus constant infusion paradigm. The purpose of these experiments was to find an appropriate procedure to expedite this analysis during routine determinations. The procedure was applied to the plasma analysis of 22 human subjects. Each plasma sample was subjected to acetonitrile protein precipitation. After separation of the pellet, the acetonitrile fraction contained 91% +/- 2% (n = 88) of the mixture of labeled metabolites and parent compound. The recovery coefficient of unmetabolized [123I]IBZM determined with an standard plasma sample was 95% +/- 2% (n = 22). The percent parent compound present in the extracted fraction, measured by high performance liquid chromatography, was 16% +/- 9% (n = 85) and the percent metabolites was 84% +/- 9% (n = 85). Free fraction determination (f1, fraction of radiotracer unbound to protein), was 4% +/- 0.8% (n = 22). Free fraction of parent was 15% +/- 8% (n = 85). The results indicate that acetonitrile protein precipitation is an adequate method for the analysis of the [123I]IBZM plasma metabolites.
authors.affiliation: Department of Psychiatry, Columbia University College of Physicians and Surgeons, and New York State Psychiatric Institute, New York 10032, USA. Yolanda@neuron.cpmc.columbia.edu
authors.forename: Y
authors.initials: Y
authors.lastname: Zea-Ponce
authors.forename: M
authors.initials: M
authors.lastname: Laruelle
mesh_terms: D000085:Acetates; D000097:Acetonitriles; D001549:Benzamides / Q000097:blood*; D001798:Blood Proteins / Q000032:analysis* / Q000378:metabolism; D011232:Chemical Precipitation; D002623:Chemistry Techniques, Analytical / Q000379:methods; D018492:Dopamine Antagonists / Q000097:blood*; D006801:Humans; D007457:Iodine Radioisotopes; D011759:Pyrrolidines / Q000097:blood*; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D050637:Receptors, Dopamine D3; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D000085:Acetates; D000097:Acetonitriles; D001549:Benzamides; D001798:Blood Proteins; C493593:DRD3 protein, human; D018492:Dopamine Antagonists; D007457:Iodine Radioisotopes; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; C007650:ethyl acetate; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide; C032159:acetonitrile