Immunocytochemical localization of ornithine decarboxylase in cultured murine cells

Antiserum elicited to ornithine decarboxylase (ODC) purified from murine RAW 264 macrophage-like cells has been employed to localize ODC in cultured murine cells. The antiserum immunoprecipitated 100% of the ODC activity from the cultured cells. The specificity of the antiserum was demonstrated by the immunoprecipitation from 35S-methionine metabolically-labeled cell extracts of a single protein which migrated upon SDS-gel electrophoresis coincident with authentic ODC. Indirect immunofluorescence experiments were performed on paraformaldehyde-fixed RAW 264 cells and JB6 epidermal cells using the rabbit anti-ODC antiserum and FITC-conjugated goat anti-rabbit IgG. Little immunofluorescence was apparent in non-stimulated cells. Intense immunofluorescence was detectable in stimulated cells at times of peak cellular ODC activity. Antigenically-reactive ODC was localized diffusely in the cytoplasm and was absent in the nuclei of RAW 264 cells, whereas in the JB6 cells the immunodetectable enzyme protein was localized in a punctate pattern in both the cytoplasm and nucleoplasm and was absent in the nucleolus. The appearance and disappearance of immunoreactive ODC in both cell types after stimulation was consistent with the alterations in ODC activity.