Epoxide hydrolase is a marker for the smooth endoplasmic reticulum in rat liver

Epoxide hydrolase (EH, EC 3.3.2.3) was chosen as a potential marker for smooth endoplasmic reticulum, because this enzyme is inducible by drugs such as phenobarbital. The hypothesis was verified in rat liver using immunochemical and immunocytochemical techniques. Antibodies were raised to the purified protein. These antibodies were affinity purified using the enzyme immobilized on Sepharose Ultrogel. The specificity of the antibodies was assayed by immunoelectrotransfer (Western blot). The labelling of rat liver thin frozen sections with protein A-gold particles demonstrated that the antibodies specifically recognised smooth endoplasmic reticulum membranes. Rough endoplasmic reticulum, other intracellular organelles and plasma membrane were unlabelled.