Distribution of gastrin in canine, cat, and human digestive organs

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

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.

Glycine-extended post-translational processing intermediates of gastrin and cholecystokinin in the gut

Cholecystokinin (CCK) and gastrin are two polypeptide hormones of the gut that share complete structural homology in their carboxyl-terminal pentapeptide. Both peptides are biologically activated from their glycine-extended precursor forms by a carboxyl-terminal alpha-amidation reaction. In the present studies we used region specific antisera to characterize the carboxyl-terminally amidated and glycine-extended forms of gastrin and CCK in mammalian intestine. Multiple amidated molecular forms of gastrin and CCK and their corresponding glycine-extended forms were detected throughout the most of the small bowel. Although, we detected substantial amounts of glycine-extended CCK in the proximal rat duodenum, we detected none of the corresponding amidated molecular forms. In contrast, the proximal duodenum of dog and hog contained both glycine-extended and amidated CCK. These findings suggest that there may be peptide, tissue and species specific differences in expression and activity of the peptide alpha-amidating enzyme.

Effects of truncal vagotomy on tissue gastrin content and G cell density in rats

Tissue and serum immunoreactive gastrin (IRG) concentrations were measured by radioimmunoassay, and antral G cell density was studied by immunofluorescence in seven non-operative and ten vagotomized (one month postoperatively) rats. In the non-operative rats, tissue IRG concentration was overwhelmingly high in the antrum, especially in the distal antrum, and much less in the small intestine, in which it tended to be lower toward the distal part. There were no significant differences between the vagotomized and non-operative rats in antral G cell density, antral tissue IRG concentration, total IRG content of the anterior antrum and serum IRG level, although significantly increased wet weight of the specimen, which was considered a result of the operation, was observed in vagotomized rats. The presence of G cell hyperplasia after vagotomy cannot be confirmed from our one-month postoperative observations in rats.