Microsomal glutathione transferase 1 (MGST1) is an abundant protein that catalyzes the conjugation of electrophilic compounds with glutathione, as well as the reduction of lipid hydroperoxides. The level of MGST1 mRNA in rat are highest in liver, while the levels of expression vary in non-hepatic tissues. In addition, the subcellular localization patterns of MGST1 are highly tissue specific. In hepatocytes and bile ducts, MGST1 is localized to the cytoplasm. MGST1 is localized to the nucleus in choroid plexus and primary spermatocytes and displays a granular cytoplasmic staining pattern in the adrenal medulla). Also, focal staining of MGST1 is observed in the distal tubules and collecting ducts of the liver.