The G-cells in the dog: a light and electron microscope immunocytochemical study

Abstract

An immunohistochemical study has been performed to analyse the distribution of gastrin cells in the gastrointestinal tract of the dog. This study revealed that G-cells immunoreactive for gastrin were almost exclusively present in the pyloric antral mucosa, mainly in the middle third of the pyloric mucosa. The calculated number of G-cells per surface unit area was 8.5 x 10(3)-1.2 x 10(4) cells cm-2. Some gastrin-immunopositive cells were found in the first 10 mm of the proximal duodenum, mainly in the villous region. The fundic area of the dog stomach, the oesophagus, small intestine, caecum, colon, rectum, salivary glands, liver and pancreas were all immunonegative for gastrin. At the ultrastructural level, three different types of granules (150-400 nm) were evident in G-cells: electron-dense, electron-lucent and intermediate forms. Most of them were located in the subnuclear region of the cell. The effect of fixation of the antral mucosa at different pH levels was studied. In samples fixed with acid solutions, most of the G-cell granules were of the electron-dense type and were strongly immunopositive for gastrin. Fixation of samples at a basic pH resulted in most of the gastrin granules losing their contents into the cytoplasm, and the positive reaction to gastrin was then located in the cytoplasm and at the periphery of the electron-lucent granules.

Ultrastructural Staining with Sodium Metaperiodate and Sodium Borohydride

“…We have observed that some postembedding immunocytochemical methods, which involve the incubation of sections in sodium metaperiodate and sodium borohydride solutions before immunolabeling (Lobo et al 2000a), result in chromatin bleaching. However, the immunogold methods used in other studies that included the use of sodium metaperiodate but not sodium borohydride (Galán et al 1996;Lobo et al 1997;Goldstein et al 1999) provide an electron-dense contrast to chromatin masses. This observation led us to develop new procedures as simple and reproducible staining methods for the cell nucleus and other cellular structures.…”