Paneth cells and goblet cells express the neuroendocrine peptide synaptophysin. I. Normal duodenal mucosa.

Paneth cells are known to produce lysozyme, α-defensins, phospholipase, matrilysin and guanylin. This study reports, for the first time, that duodenal Paneth cells may also produce the neuroendocrine peptide synaptophysin. Normal duodenal biopsies from 37 patients were immunostained for synaptophysin and lysozyme. Synaptophysin was expressed in Paneth cells, in goblet cells (in the mucus and cytoplasm) and in the neurons/synapses in the mucosa and submucosa. Mucous glands in the submucosa (Brunner's glands) were synaptophysin negative. Lysozyme was expressed in Paneth cells, goblet cells (in the mucus but not in the cytoplasm) and in the mucous glands in the submucosa. Lysozyme was not expressed in the cytoplasm of goblet cells, nor in the neurons/synapses of the mucosa and submucosa. The differences in expression between synaptophysin and lysozyme seem to validate the immunospecificity of synaptophysin. The finding that synaptophysin is also produced by Paneth cells adds new information which might help to unravel the riddle of the ultimate biological significance of these puzzling cells.