Immunocytochemical localization of gamma-glutamyltransferase in rat kidney with protein A-horseradish peroxidase.

Immunocytochemistry with a specific antiserum and protein A-horseradish peroxidase permits visualization of the sites of gamma-glutamyltransferase [(5-glutamyl)-peptide:amino-acid 5-glutamyltransferase, EC 2.3.2.2] at both the light- and the electron-microscope levels. As seen by light microscopy, the enzyme is localized only in the proximal convolutions of the renal tubules. Electron microscopy reveals dense deposits of 3,3'-diaminobenzidine reaction product embedded in the glycocalyx along the entire luminal surface of the microvilli and in the basolateral membranes.