Production and secretion of pancreatic secretory trypsin inhibitor in normal human small intestine

The aim of this study was to prove the production and secretion of pancreatic secretory trypsin inhibitor (PSTI) in human small intestine. To achieve this we analyzed the content of immunoreactive PSTI (irPSTI) in rinsing fluid from isolated small intestine, using the urea method to estimate the volume of epithelial lining fluid recovered. IrPSTI, measured by an enzyme-linked, immunosorbent assay (ELISA), was present in both free and complexed form. The free PSTI showed intact biologic activity, binding trypsin in stable complexes. The complexed PSTI was dissociated on acidification. With the reverse transcriptase polymerase chain reaction (RT-PCR) and Southern blot hybridization, PSTI mRNA was demonstrated in the mucosa of the ileum. These findings indicate that PSTI is produced and secreted in the small intestinal epithelium and may be part of defence system in intestinal mucosa.