Immunohistochemical localization, purification, and characterization of human urinary bladder glutathione S-transferases

This study describes immunohistochemical localization, purification and characterization of glutathione S-transferase (GST) of human urinary bladder. Even though all the three major classes of isoenzymes (α, μ, and π) were expressed in human bladder, more than 90% of total GST activity was accounted for by a π class anionic form. Human bladder α, μ, and π class GSTs were immunologically related to respective isoenzymes of other human tissues. GST π was present in all 13 samples analyzed, whereas GST α and μ were detected in nine and eleven samples, respectively. GST α of human bladder appeared to be unique, because unlike this class of GSTs of other human tissues, bladder enzyme had lower affinity for GSH linked to epoxy-activated Sepharose 6B affinity resin. Immunohistochemical staining indicated localization of GST α in epithelial surface cells, underlying submucosa and smooth muscle, whereas μ and π class isoenzymes were predominantly distributed in epithelial surface cells. These results suggest that human bladder GSTs may play an important role in providing protection against xenobiotics because epithelium is considered a target for several carcinogens and all the three classes of isoenzymes are expressed in these cells.