LOCALIZATION OF MICROSOMAL EPOXIDE HYDROLASE IN NORMAL AND NEOPLASTICHUMAN KIDNEY

Microsomal epoxide hydrolase is a xenobiotic metabolizing enzyme that catalyzes the conversion of toxic and carcinogenic epoxides to less to xic dihydrodiols, The cellular localization and distribution of micros omal epoxide hydrolase were investigated for the first time in normal and neoplastic human kidney. Light microscopic immunohistochemical stu dies using an alkaline phosphatase-anti-alkaline phosphatase technique showed that in normal kidney there was a wide distribution of epoxide hydrolase immunoreactivity, The main localization of epoxide hydrolas e immunoreactivity was to the proximal and distal tubule epithelial ce lls, Strong epoxide hydrolase immunoreactivity was also identified in epithelium of the collecting ducts, In addition, epoxide hydrolase imm unoreactivity was present in vascular endothelial cells, including end othelial cells lining glomerular capillaries. Epoxide hydrolase immuno reactivity was identified in all the renal tumors, and in each tumor i mmunoreactivity for epoxide hydrolase was localized to tumor cells. Im munoblotting of both normal kidney and tumor microsomes confirmed the presence of a single protein band of molecular weight 49 KD correspond ing to the molecular weight of human hepatic microsomal epoxide hydrol ase.