MAPPING OF INTRACELLULAR HALOGENOUS MOLECULES BY LOW AND HIGH-RESOLUTION SIMS MICROSCOPY

The subcellular distribution of halogenous molecules has been studied by SIMS microscopy in cultured cells of a human breast carcinoma (MCF- 7 cell line). Two instruments of microanalysis were used. A low latera l resolution ion microscope (SMI 300 CAMECA) and a prototype scanning ion microscope equipped with a cesium gun that gives high lateral reso lution images. This apparatus has been developed by G Slodzian, in One ra Laboratories (Office National d'Etudes et de Recherches Aerospatial es). Molecules studied by low lateral resolution ion microscope were h alogenous steroids: fluorometholone, triamcinolone, bromocriptine and bromoandrosterone. Analytical images show that the first two compounds are mainly localized in the nuclear structure of MCF-7 cells whereas the last two molecules are localized in cytoplasm of these cells. Imag es were obtained with a resolution of 1-mu-m. With the scanning ion mi croscope, it is now possible to obtain images at the ultrastructural l evel. Four analytical images can be simultaneously obtained by a singl e scan of the imaged area, corresponding to a depth of erosion of the section of ten nm. The intranuclear distributions of three pyrimidine analogs, 5-bromo-2'-deoxyuridine, 5-iodo-2'-deoxyuridine and 5-fluorou racil have been studied in phase S and M of MCF-7 cells and these imag es have been compared to the distribution of sulfur, nitrogen and phos phorus. All these images have been obtained with a lateral resolution better that 100 nm.