Localization of cholesterol in rat cerebellum with imaging TOF-SIMS Effect of tissue preparation

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was utilized to address the issue of cholesterol localization in rat cerebellum, a subject not previously investigated. Rat cerebellum was prepared by three different procedures: (1) fixation in formaldehyde, freeze-protection by sucrose, freezing in liquid nitrogen and sectioning by cryoultramicrotomy and drying at room temperature or (2) freezing in liquid nitrogen, cryostat sectioning at −40 °C and drying at room temperature or (3) high-pressure freezing, freeze-fracturing and freeze-drying. The samples were analyzed in an imaging TOF-SIMS instrument equipped with a Bi1–7+-source. The cholesterol signal (m/z 369 and 385), showed high intensity in the glial cells in white matter and lower intensity in Purkinje cells and in nuclei of granular layer cells. Specimen treated by procedure 1 showed some signs of diffusion of cholesterol in the tissue. Specimen treated by procedure 2 showed freeze-damage of the cells. Specimen treated by procedure 3 showed distinct localization of cholesterol in well preserved tissue. Thus, high-pressure freezing and freeze-fracturing was used for further characterization of the distribution of cholesterol in rat cerebellum.