Presence of sorbin in human digestive tract and endocrine digestive tumours

Background--Sorbin, a 153 amino acid peptide isolated from porcine intestin e, was localised by immunohistochemistry in endocrine cells of the intestin al mucosa and pancreas and in the enteric nervous system in the pig. Aims--To identify sorbin cells in normal human digestive tissues and to exp lore the expression of sorbin in 37 digestive endocrine tumours: 14 intesti nal carcinoid tumours and 23 endocrine pancreatic tumours including six ins ulinomas. Methods--Two polyclonal antibodies against the C-terminal and the N-termina l sequences of porcine sorbin raised in rabbit were used to evaluate sorbin expression by immunohistochemistry. Results--In the human digestive tract, sorbin, characterised by both C-term inal and N-terminal immunoreactivity, was found in enterochromaffin cells o f the gastric and intestinal epithelium from the pyloric junction to the de scending colon. C-Terminal sorbin immunoreactivity alone was found in plexi i from the enteric nervous system and in some insulin-containing cells of n ormal pancreas. C-Terminal and N-terminal antibodies disclosed sorbin in fi ve of 14 intestinal carcinoid tumours; C-ternrinal antibody alone disclosed a C-terminal sorbin peptide in two of six insulinomas and three of 17 endo crine pancreatic tumours. The presence of sorbin was not associated with a specific clinical syndrome. Conclusions--Sorbin is present in the digestive tract in several forms. It is expressed in some intestinal and pancreatic endocrine tumours.