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Competition of nitroxyl contrast agents as an in vivo tissue redox probe: Comparison of pharmacokinetics by the bile flow monitoring (BFM) and blood circulating monitoring (BCM) methods using X‐band EPR and simulation of decay profiles
Author(s) -
Okajo Aya,
Matsumoto Kenichiro,
Mitchell James B.,
Krishna Murali C.,
Endo Kazutoyo
Publication year - 2006
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.20958
Subject(s) - nitroxyl , in vivo , chemistry , blood flow , redox , pharmacokinetics , electron paramagnetic resonance , biophysics , nuclear magnetic resonance , contrast (vision) , pharmacology , photochemistry , medicine , biology , inorganic chemistry , physics , microbiology and biotechnology , artificial intelligence , computer science
Nitroxyl radicals used as tissue redox‐sensitive contrast agents in electron paramagnetic resonance (EPR) and/or NMR imaging should satisfy the following two conditions: 1) the molecules disperse into tissues rapidly, and 2) paramagnetic loss occurs by simple reduction of the radical. The pharmacokinetic trends of several nitroxyl contrast agents were compared with the results obtained by bile flow monitoring (BFM) and blood circulation monitoring (BCM) methods using X‐band EPR. The nitroxyl radicals (TEMPO, TEMPONE (oxo‐TEMPO), and amino‐TEMPO) showed additional EPR signals in the bile that were attributed to metabolites formed during transport from blood to bile through the liver. However, the highly hydrophilic CAT‐1 (trimethylammonium‐TEMPO), which has low membrane permeability, showed minimal concentration in the bile. Probes that have carboxyl moiety, such as carboxy‐TEMPO and carboxy‐PROXYL, can be transported via anion transporter into hepatic cells. The EPR signal decay profiles of the nitroxyl radicals were simulated based on the experimental data. The simulation, which we previously applied to mouse blood, was modified to simultaneously fit the experimental results of BFM and BCM obtained with rats. The simulation data showed the simplicity/complexity of the pharmacokinetic mechanisms and that carbamoyl‐PROXYL and TEMPOL (hydroxy‐TEMPO) are suitable contrast agents for assessing tissue redox status. Magn Reson Med, 2006. Published 2006 Wiley‐Liss, Inc.