INHIBITION OF UNSTIMULATED EXOCRINE PANCREATIC-SECRETION BY PEPTIDE YY IN THE RAT

Peptide YY is an ileocolonic peptide known to inhibit postprandial and cholecystokinin-induced pancreatic exocrine secretion. It has also be en shown to increase intestinal water and electrolyte absorption. Thes e findings implicate PYY as being potentially useful for controlling w atery diarrhea. Although its inhibitory effect on stimulated pancreati c secretion has been well established, PW effects on interdigestive, u nstimulated pancreatic secretion is not known. This study was designed to evaluate the effect of PW on basal pancreatic exocrine secretion i n a conscious rat. Male Sprague-Dawley rats were prepared with cathete rs for internal biliary bypass, pancreatic juice collection, and intra duodenal reinfusion of pancreatic juice. Jugular and carotid catheters were inserted for drug infusions and blood sampling. After overnight recovery, fasting rats were infused over 6 hours with saline or PYY (4 00 or 800 pmol/kg/hr). Pancreatic juice was measured and sampled at 60 -minute intervals for volume and its protein and bicarbonate content. The remainder was reinfused into the duodenum. Before and after the ex periment, pancreatic juice was automatically reinfused by a photocell- controlled peristaltic pump system. Intraductal pancreatic secretion w as not affected by PW at a dose of 400 pmol/kg/hr. PYY at a dose of 80 0 pmol/kg/hr significantly reduced the volume of pancreatic secretion and its protein and bicarbonate content. Pancreatic secretory response normalized within 24 hours. In conclusion, unstimulated pancreatic ex ocrine secretion can be inhibited by exogenous PW in the rat.