Development of a procedure for autoradiographic localization of carbonic anhydrase at the electron microscope level

A method for preparing tissue suitable for electron microscope autoradiographic localization of carbonic anhydrase is described. Radioactivity is in the form of 3H-acetazolamide, a specific inhibitor of carbonic anhydrase. Tissues fixed in glutaraldehyde, dehydrated in ethylene glycol followed by cellosolve as a transition fluid, and embedded in epoxy resin, were found to retain most (74%) of the label. Electron micrographs of avian gastric mucosa prepared in this manner are shown. Other methods of preparation were explored and resulted in considerable losses of label or in inadequately preserved tissue. Light microscope autoradiographic localization of gastric mucosa, shell gland, chorioallantoic membrane, and skeletal muscle compare well with previous localizations.