Phytohaemagglutinin stimulates pancreatic enzyme secretion in rats by a combination of cholecystokinin- and noncholecystokinin-linked pathways

Kidney bean (Phaseolus vulgaris) E2L2 lectin (PHA) given orally to rats or continually infused into the duodenum of both anaesthetised and conscious r ats stimulated the secretion of cholecystokinin (CCK) from gut enteroendocr ine (I) cells and of digestive enzymes from the pancreas. PHA also stimulat ed the release of CCK from duodenal I cells in vitro. The pancreatic secret ory response to PHA in the early stages was mainly independent of CCK media tion. At later stages, additional mechanisms, not directly involving CCK, a lso appeared to play a role in modulating exocrine pancreatic responses to PHA. In addition to its effects of CCK-secreting I cells, PHA could stimula te or inhibit the release of other gut hormones which are important in over all regulation of exocrine pancreatic metabolism. As a result the PHA-induc ed CCK release and pancreatic growth could be effectively uncoupled from th e synthesis of digestive enzymes in the pancreas and their secretion into t he duodenum. In addition, systemically absorbed PHA may also have some slig ht role in directly triggering enzyme secretion from pancreatic acini. All these PHA effects were in contrast to the known CCK-mediated stimulatory ef fects of soya bean trypsin inhibitors, which were fully abolished after tre atment with L-364718.