Ontogeny, distribution and amine/peptide content of chromogranin A- and B-immunoreactive endocrine cells in the small and large intestine of the chicken

Chromogranin A-(CgA-) and chromogranin B-(CgB-)-immunoreactive endocrine cells were investigated in the chicken intestine during embryonic and post-hatching life. CgA- and CgB-immunoreactive cells first appeared in the intestinal tract at various embryonic ages from day 10 in the cloaca to day 16 in the distal ileum and colon. To identify the CgA- and CgB-immunoreactive cells, each tissue section was double-immunostained using a panel of polyclonal antibodies raised against gut amine/peptides. Almost all the serotonin-immunoreactive cells co-localised CgA and CgB along the entire intestinal mucosa and at all ages examined. In contrast, substance P-, peptide tyrosine tyrosine-, neurotensin- and secretin-immunoreactive cells displayed heterogeneous co-localisation patterns. For example, either all or only some cells of a given endocrine type co-stored Cg; they did so variously-only in the embryo, only after hatching, or at both stages, and co-localizing cells were sometimes located within the mucosa only in the villi and not in the glands, and sometimes vice versa. All the CgA/CgB-immunoreactive cells also displayed argyrophilia.