Image analysis of the duodenal endocrine cells in mice with particular regard to optical densitometry

The endocrine cells in the murine proximal duodenum have been investigated by means of immunohistochemistry and computerized image analysis. Five endocrine cell types were identified, namely secretin-, gastric inhibitory polypeptide (GIP)-, gastrin-CCK-, somatostatin- and serotonin immunoreactive cells. The number of endocrine cells/mm3 epithelial cells was estimated and the cell secretory index (CSI) for different endocrine cell types was determined. Furthermore, the optical density of the cellular immunoreactivity and the immunoreactive area in the cell were determined and an index, cell immunoreactivity content was estimated as the optical density multiplied by the immunoreactive area. It has been suggested that the use of this index might better reflect the cellular peptide/amine content than does the CSI. Serotonin-immunoreactive cells were the predominant endocrine cell type, followed by gastrin/CCK-immunoreactive cells. The numbers of secretin-, GIP- and somatostatin immunoreactive cells were almost identical. All endocrine cell types were present both in crypts and in villi, but were, more numerous in the crypts, except for secretin which was more frequent in the villi.