In vitro degradation of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) by cytosolic enzymes of Japanese quail and the rabbit

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DOIResolve DOI: http://doi.org/10.1897/06-068R.1
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TypeArticle
Journal titleEnvironmental Toxicology and Chemistry
Volume25
Issue12
Pages32213229; # of pages: 9
SubjectAdult; analysis; Animal; Animals; Brain; env; Enzymes; In Vitro; Liver; Protein
AbstractHexanitrohexaazaisowurtzitane (CL-20) is a polycyclic nitramine explosive and propellant, currently being considered as a potential replacement for existing cyclic nitramine explosives. Earlier studies have provided evidence suggestive of adverse liver effects in adult Coturnix spp. exposed to CL-20, yet analysis of tissue samples (plasma, liver, brain, heart, or spleen) indicated that CL-20 was not detectable in these treated animals. The present study was conducted to identify and purify the enzymes capable of CL-20 biotransformation. Results indicate that the hepatic biotransformation of CL-20 in vitro was inhibited by ethacrynic acid (93%) and by the glutathione (GSH) analogue S-octylglutathione (80%), suggesting the involvement of glutathione-S-transferase (GST). Partially purified cytosolic ?- and ?-type GST (requiring presence of GSH as a cofactor) from quail and rabbit liver was capable of CL-20 biotransformation. The degradation of CL-20 (0.30 � 0.05 and 0.40 � 0.02 nmol/min/mg protein for quail and rabbit, respectively) was accompanied with the formation of nitrite and consumption of GSH. Using liquid chromatography/mass spectrometry, we detected two intermediates, that is, open-ring, monodenitrated GSH�conjugated CL-20 biotransformation product with the same deprotonated molecular mass ion at 699 Da, suggesting isomeric forms of the intermediate metabolites. Identity of the conjugated metabolites was confirmed by using ring-labeled [15N]CL-20 and the nitro group�labeled [15NO2]CL-20. These data suggest that the in vitro biotransformation of CL-20 by GST under the conditions tested may be a key initial step in the in vivo degradation of CL-20 in the quail and resulted in the formation of more biologically reactive intermediates than the parent compound. These data will aid in our understanding of the biotransformation processes of CL-20 in vivo.
Publication date
LanguageEnglish
AffiliationNRC Biotechnology Research Institute; National Research Council Canada
Peer reviewedNo
NRC number47276
NPARC number3540310
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Record identifierf9bc966d-3da1-481e-8fd6-866f4dca2c5d
Record created2009-03-01
Record modified2016-05-09
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