Morphological variation of immunoreactive cells positive to cholecystokinin 33 (10-20) and gastrin 34 (1-15) in human duodenum.

Human duodenal endocrine cells reactive with antibodies to cholecystokinin (CCK) 33 (10-20) and/or gastrin 34 (1-15) were studied by a combination of immunohistochemical and electron-microscopic methods. By immunohistochemistry, three types of endocrine cells were distinguished in human duodenal mucosa, i.e., those only positive for only CCK, those positive for both CCK and gastrin and those only positive for only gastrin. Ultrastructurally, the first cell type is characterized by many secretory granules with an eccentric dense core (mean diameter; 271 +/- 74 nm). The second cell type, which was less frequent than the other two, has ultrastructural features that resemble type-I cells. The last cell type was composed of two types of cells containing small secretory granules identical to those of IG cells (mean diameter; 171 +/- 31 nm) or large secretory granules indistinguishable from those of I cells (mean diameter; 286 +/- 50 nm).