Effects of Exogenous Secretin on Pancreatic and Biliary Ductal and Sphincteric Pressures in Man Demonstrated by Endoscopic Manometry and Correlation with Plasma Secretin Levels

An endoscopic manometric technique was used to investigate the effects of exogenous secretin on pancreatic duct, common bile duct, pancreatic duct sphincter, and bile duct sphincter pressures in 20 healthy volunteers. Synthetic secretin was infused intravenously at rates of 8.05, 16.1, 32.2, 64.4, 129, 258, and 516 ng/kg/hr, and plasma secretin concentrations were measured by a radioimmunoassay. Secretin produced a significant fall in peak and trough pancreatic duct sphincter pressures from basal values of 48.2 +/- 7.9 mm Hg (mean +/- SD) and 16.9 +/- 7.7 mm Hg, respectively, to 34.4 +/- 6.8 mm Hg and 11.2 +/- 5.8 mm Hg (P less 0.005), respectively, at a mean plasma secretin concentration of 16 pg/ml (during an infusion rate of 32.2 ng/kg/hr). Higher infusion rates had no additional effect. Pancreatic duct pressure became significantly elevated above basal (11.5 +/- 4.0 mm Hg) at the two highest secretin rates. Secretin had no effect on common bile duct or bile duct sphincter pressures. Plasma secretin concentrations were within the postprandial range during the lowest four secretin infusion rates. We conclude that secretin produces selective physiological relaxation of the pancreatic duct sphincter.