Abstract
An approach to the localization of isotopically labelled lipid-soluble and water-soluble substances by autoradiography is presented. Previous attempts to retain such substances in situ in tissues have often been unsuccessful due to diffusion in the media involved in tissue preparation; and at the interface between the emulsion and the tissue section. Rats were given estradiol-H3 and aspirin-H3 as representatives of lipid-soluble and partially water-soluble compounds. After removal, tissues were quick frozen, frozen-dried, fixed in the vapor phase with osmium tetroxide or paraformaldehyde and vacuum embedded in Epon. One-micron sections were coated with emulsion and subsequently developed. Discrete localization of isotope was seen in autoradiographs. Data is presented to demonstrate the marked solubility of these compounds in the media used for routine fixation and dehydration, in contrast to their insolubility in epoxy resin. These findings present an opportunity for the cellular localization of numerous compounds by autoradiography that heretofore has not been possible.