Epithelial and neuronal calbindin in avian intestine. An immunohistochemical study

It is well known that calbindin immunoreactivity is highly concentrated in the duodenal absorptive cells of young birds. We have shown that in the adult intestine of three avian species, calbindin content is much more variable. In addition to absorptive cells, we have detected throughout the gut of both sexes of the domestic fowl and in the large intestine of the Japanese quail a second type of calbindin-positive epithelial cell which has the shape of a typical endocrine cell. These cells were particularly abundant in the large intestine, in contrast to the usual distribution of endocrine cells along the gut. Calbindin was also detected in the nervous system of the intestine. Calbindin-positive nerve fibres were rare in the duodenum and ileum, numerous in plexuses and nerve processes in both muscular layers and lamina propria of the large intestine in domestic fowl and Japanese quail. In the mallard, nerve fibres were rarely calbindin positive while definitively positive for VIP. Calbindin of the peripheral nervous system of the domestic fowl and Japanese quail comigrates with the duodenal calbindin (27,000 dalton) in SDS gel electrophoresis.