Cholecystokinin-induced persistent stimulation of enzyme secretion from pancreatic acini

When pancreatic acini are first incubated with cholecystokinin, washed to remove free cholecystokinin and then reincubated in fresh incubation solution, there is significant residual stimulation of amylase secretion. This residual stimulation requires relatively high concentrations of the secretagogue, is reversible, and is specific for cholecystokinin. Induction of residual stimulation occurs more rapidly at 37 degrees C (maximal by 1 min) than at 4 degrees C (maximal by 10 min), and, once induced, residual stimulation persists for up to 75 min at 37 degrees C and for more than 90 min at 4 degrees C. The persistent effect of cholecystokinin on enzyme secretion cannot be accounted for by incomplete removal of the secretagogue by the wash procedure or by activation of some intermediate step in the mechanism of action of cholecystokinin that persists after the secretagogue dissociates from its receptors. Instead, cholecystokinin-induced residual stimulation of enzyme secretion appears to result from persistent occupation of cholecystokinin receptors by the secretagogue.