Received for publication August 1, 2007.
Revised September 4, 2007.
Accepted for publication September 7, 2007.

Generation and functional characterization of mice with a disrupted glutathione S-transferase, theta 1 gene

Abstract

Glutathione S-transferase Theta 1 (GSTT1) has been regarded as one of the key enzymes involved in phase II reactions because of its unique substrate specificity. In this study, we generated mice with disrupted glutathione S-transferase, theta 1 (Gstt1) gene (Gstt1-null mice) by gene targeting, and analyzed the metabolic properties in cytosolic and in vivo studies. The resulting Gstt1-null mice failed to express the Gstt1 mRNA and GSTT1 protein by RT-PCR analysis and 2-dimensional fluorescence difference gel electrophoresis/mass spectrometry analysis, respectively. However, the Gstt1-null mice appeared to be normal and were fertile. In an enzymatic study using cytosolic samples from the liver and kidney, GST activity toward 1,2-epoxy-3-(p-nitrophenoxy)propane (EPNP), dichloromethane (DCM) and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) was markedly lower in Gstt1-null mice than in the wild-type controls, in spite of there being no difference in GST activity toward 1-choloro-2,4-dinitrobenzene between Gstt1-null mice and the wild-type controls. Gstt1-null mice had GST activity of only 8.7 to 42.1% of the wild-type controls to EPNP, less than 2.2% of the wild-type controls to DCM and 13.2 to 23.9% of the wild-type controls to BCNU. Plasma BCNU concentrations after a single intraperitoneal administration of BCNU to Gstt1-null mice were significantly higher and there was a larger AUC5-60 min (male, 2.30 times; female, 2.28 times, versus the wild-type controls) based on the results. In conclusion, Gstt1-null mice would be useful as an animal model of humans with GSTT1-null genotype.

Key words: genetic polymorphism, glutathione transferases, phase II drug metabolism, proteomics, recombinant DNA technology, transgenic models