Calretinin and calbindin-D28k immunoreactivity in the human gastrointestinal tract

Calretinin and calbindin-D28k are similar Ca(2+)-binding proteins previously described in specific central neurons and other cells.

The immunocytochemical distribution of these two proteins was studied in the human gastrointestinal tract.

In gastric and small intestinal endocrine cells, calbindin-D28k immunoreactivity was confirmed, but calretinin immunoreactivity was not found. Nerve cell bodies in both submucous and myenteric ganglia were immunoreactive for calbindin (13% and 38% of total cells, respectively) or calretinin (23% and 21%), some containing both proteins. In nerve processes, calretinin was generally more abundant than calbindin and was found particularly around blood vessels. Calretinin co-localized with immunoreactive vasoactive intestinal peptide, neuropeptide Y, galanin, or substance P in submucous ganglion cells and with substance P in myenteric cells. Calbindin-D28k colocalized with fewer peptides, specifically vasoactive intestinal peptide or galanin in submucous cells. By 8 weeks of fetal development, discrete neuronal localizations for both proteins and for calbindin-D28k in endocrine cells were apparent.

In the enteric neuroendocrine system, calretinin and calbindin-D28k are useful markers that may help elucidate Ca(2+)-mediated functions in health and disease.