SIMS MICROSCOPY - A TOOL TO MEASURE THE INTRACELLULAR CONCENTRATION OF CARBON-14-LABELED MOLECULES

Monolayer cultures of human fibroblasts were incubated for 24 h with C -14-arginine and observed by means of SIMS microscopy (ion microscopy) . Carbon 14 imaging showed the intracellular distribution of labelled arginine which featured high nuclear incorporation. The local concentr ation of this amino acid in different cells and intracellular structur es was assessed through local isotopic C-14/C-12 ratio measurement. Th is relates the signal intensity of the labelling isotope carbon 14 to that of the corresponding natural isotope (carbon 12) of known tissula r concentration. Using this method we were able to measure minor varia tions in the molecular concentration of arginine (expressed as mu-mol/ g of tissue) between different fibroblasts. Results of this study indi cate that SIMS microscopy is well adapted to carbon 14 detection and c an provide quantitative maps of the cellular and subcellular distribut ion of C-14-labelled molecules.