Fatty-acid transport in cultured adipocytes. (a-i) MIMS mass images of cells dried with argon after unwashed 3T3F442A adipocytes were incubated with 13C- oleate. Images show (a) 12C-, (b) 13C-, (d) 12C14N-, and (e) 12C15N-, and their respective ratio images of (c) 13C-/12C- and (f) 12C15N-/12C14N-. (g) HSI image of the 13C-/12C- ratio (the numerator has been multiplied by 100); (h) an RDIC image of the same cells before analysis with MIMS. RDIC images (500×) were obtained using a Nikon Eclipse E800 upright microscope. (i) The 13C14N-/12C14N- distribution also reveals the excess 13C in the lipid droplets. O, outside the cells; I, inside but not in visible lipid droplets; LD, inside the lipid droplets. The MIMS images are 60 × 60 μm (256 × 256 pixels) and were acquired in 40 min. (j) HSI of the 13C/12C ratio after 'shaving' (see text) the adipocyte shown in (a-i); the adipocyte had been exposed to a high primary-ion beam current approximately 1,000-fold more intense than for the previous analysis to quickly remove material from the sample surface in order to analyze deeper within the cell. Field: 60 × 60 μm (256 × 256 pixels); acquisition time 10 msec/pixel. (k) Bar graph of the mean and standard deviation values of the 13C-/12C- ratio in 3T3F442A adipocytes. O, outside the cells; I, inside but not in visible lipid droplets; LD, inside the lipid droplets. 13C-/12C- ratio values are shown after subtraction of the natural abundance ratio (1.2%). Adapted with permission from .