Ontogeny and distribution of gastrin cells in the gastrointestinal tract of the sheep.

Indirect immunofluorescence and peroxidase-antiperoxidase methods were used to analyze the development and distribution of gastrin-producing cells in 24 embryos and fetuses (at 26-120 days of prenatal life) of sheep and in 10 newborn sheep. Plasma gastrin concentrations were measured by radioimmunoassay in blood samples taken for the immunocytochemical study. Gastrin cells first appeared at 69 and 77 days of gestation in the duodenum and pyloric antrum, respectively. Gastrin immunoreactive cells were very numerous in the pyloric region, numerous in the duodenum, scarce in the jejunum and rare in the ileum. None were detected in the cardiac or fundic regions of the abomasum or in the colon or rectum. Plasma gastrin concentrations were first detected at 69 days, increasing gastrin levels being observed during the development stages just before birth. The differences between sheep and other species in the distribution and development of these endocrine cells are discussed.