HISTAMINE-STORING CELLS IN THE OXYNTIC MUCOSA OF THE RAT STOMACH - A TRANSMISSION ELECTRON-MICROSCOPIC STUDY EMPLOYING FIXATION WITH CARBODIIMIDE

We studied the distribution of histamine (HA) immunoreactivity in endo crine cells of the acid-producing mucosa in rat stomach with pre-embed ding immunoelectron microscopy (IEM) using an antiserum against HA. Fo ur fixation modifications were compared to optimize the ultrastructura l morphology and staining pattern with the antisera produced against c arbodiimide-conjugated HA. Fixation with 4% 1-ethyl-3(3-dimethyl-amino propyl) carbodiimide (EDCDI) combined with both 4% paraformaldehyde an d 0.1% glutaraldehyde gave superior results compared with EDCDI alone. Enterochromaffin-like (ECL) cells were easily distinguished from othe r endocrine cells in optimally fixed samples. The peroxidase endproduc t was distributed within the cytoplasm surrounding the vesicles of the ECL cells. ECL cells comprised about 75% of all endocrine cells, and about 90% of them were HA immunoreactive (HA-IR). No other HA-ER cell types were identified by EM in the basal half of the oxyntic region of rat gastric mucosa. The results suggest that a combination of EDCDI a nd aldehydes is suitable for IM demonstration of HA in cells. ECL cell s form a predominant portion of endocrine cells in the oxyntic glands and may constitute the only significant non-mast cell store of HA in r at gastric mucosa.