Bicarbonate and cyclic AMP content of pure human pancreatic juice in response to graded doses of synthetic secretin.

In seven healthy volunteers pure pancreatic juice was obtained by endoscopic cannulation of the papilla of Vater. Synthetic secretin was intravenously infused in doses doubled every 20 min. The volume of pancreatic juice was proportional to the log of the secretin dose. A significant rise (P less than 0.05) in pancreatic juice flow was elicited at a dose as low as 8.05 ng per kg per hr. Maximum flow rate approximating 250 mul per 5 min per kg of body weight was attained during infusion of 129 ng per kg per hr. At the same dose maximal bicarbonate outputs averaging 383 muEq per hr per kg of body weight were obtained, whereas bicarbonate ion concentration approached peak values (135 +/- 9 muEq per ml) at 32.2 ng per kg per hr. Bicarbonate concentrations showed a tendency to fall at supramaximal doses. The effect of increasing secretin doses on bicarbonate and cyclic AMP concentrations was remarkably similar (rs = 0.635, P less than 0.001) suggesting the participation of cyclic AMP in human pancreatic bicarbonate secretion.