Fixation with zinc-formalin as an adequate substitution of Zenker-formol for the histochemical staining of the pancreatic islet cells

AIM: The work aimed to determine the possibility of using zinc-formalin fixation instead of Zenker-formol to identify selectively all the main types of cells (A, B, D) of the pancreatic Langerhans islets by staining using classical histochemical methods. MATERIALS AND METHODS: Pancreatic samples of the naked mole rat (Heterocephalus glaber, Rppell, 1842) were fixed for 24 hours in zinc-formalin fixative containing 300 ml of 37% formaldehyde, 50 g of zinc chloride, 1.9 ml of glacial acetic acid, and 2 L of distilled water. After fixation, the standard procedures for paraffin embedding and staining with Heidenhains azan and a combination of azan and Gomoris paraldehyde-fuchsin were performed according to routine protocols. RESULTS: It was revealed that a distinctive differential staining of all three major types of islet cells can be obtained if pancreatic samples are fixed in a zinc-formalin fixative for 24 hours. At the same time, as after fixation with Zenker-formol (but not with formalin solution or Bouin fixative), not only A and B, but also D-cells are clearly identified. Comparison of the immunohistochemical data on the distribution pattern of various cells in the pancreatic islet in a naked mole rat with that detected by histochemical stains showed their complete coincidence. CONCLUSIONS: Zinc-formalin can be used as a more convenient and safer fixative for detecting Langerhans islet cells (including D cells) by staining with Heidenhains azan and Gomoris paraldehyde-fuchsin instead of mercury salt-containing Zenker-formol.