Involvement of pancreatic polypeptide (PP) in luminal feedback regulation in the conscious rat.

The possibility of the involvement of pancreatic polypeptide (PP) release in luminal feedback regulation in the conscious rat was examined. Pancreatic secretion in the intestinal phase in the rat is regulated by negative feedback control so that a decrease in luminal protease activities produced by a diversion of bile-pancreatic juice (BPJ) from the intestine stimulates pancreatic secretion. Plasma concentration of rat PP and the effect of exogenous infusion of rat PP on pancreatic secretions during BPJ diversion were determined. Plasma PP concentration significantly increased with BPJ diversion and peaked at 90 min after BPJ diversion began, almost paralleling changes in protein output. Exogenous PP infusion (1, 2 and 10 micrograms/kg/hr) inhibited pancreatic protein and fluid outputs but not the bicarbonate output during BPJ diversion. PP was shown to be physiologically released in the intestinal phase of pancreatic secretion; however, the physiological role of endogenous PP remains unknown.