Generation and expression of halothane derived protein adducts in the guinea pig liver
AuthorBrown, Alan Perry.
Committee ChairGandolfi, A. Jay
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThe volatile anesthetic halothane can be bioactivated in the liver to the reactive intermediate, trifluoroacetyl chloride, which is capable of covalently modifying liver protein. The product of this reaction is trifluoroacetyl-N-ε-amino lysine, which can act as a foreign epitope in altering both protein immunogenicity and antigenicity. Protein adduct formation appears to be responsible for the development of both an acute and an immune-mediated hepatotoxicity. The goal of this research project was to detect, quantify, and characterize the formation of protein adducts in the guinea pig liver, following exposure to halothane. This species provides the most accurate animal model for halothane hepatitis to date. An in vitro liver slice system was used to study the conditions for the production of protein adducts during halothane exposure. Covalent binding to slice protein occurred in a linear fashion over the time course of exposure, and was concentration dependent. Oxidative metabolism of halothane was required for adduct production. Adduct formation occurred to specific and identifiable proteins. The majority of the protein adducts in the liver slice were localized to cytosolic glutathione-S-transferase (GST). GST can be released from the liver slice, transporting the adduct to the extracellular environment. Guinea pigs were anesthetized with halothane to compare the results obtained in vitro, with what occurs in the whole animal. Covalent binding to liver protein occurred predominately in the microsomal fraction. The protein adducts identified in the guinea pigs corresponded to those seen in liver slices. GST was identified as a target for the acid chloride intermediate in the liver of these animals. Covalent binding to cytosolic protein was dependent on liver glutathione content. A specific relationship between adduct formation to cytosolic protein and glutathione concentration was further demonstrated using an in vitro bioactivation system. GST may catalyze the reaction between the electrophile and glutathione. Liver glutathione content appears to mediate the degree and selectivity of covalent binding to target proteins. The development of halothane induced hepatotoxicity may be related to the interactions between its reactive intermediate, glutathione, and GST.
Degree ProgramPharmacology & Toxicology