Hormonal effects on the pylorus.

The control mechanisms of pyloric pressure responses have not been elucidated clearly. The purposes of this study were twofold: 1) to determine the dose-related pressure responses of the pylorus to exogenous glucagon, secretin, and cholecystokinin, and 2) to correlate changes in pyloric pressure with serum concentrations of these hormones. Pyloric pressures were measured by infusion manometry, and the serum concentrations of glucagon and secretin were quantitated using radioimmunoassays. Each of the hormones tested, glucagon, secretin, and cholecystokinin, increased the pyloric pressure significantly. The lowest active dosages tested for each of these peptide hormones were 2 micrograms.kg-1.h-1, 2 U.kg-1.h-1, and 1 U.kg-1.h-1, respectively. The maximal pyloric pressure responses recorded were 8.7 +/- 1.1 (P less than 0.05), 12.6 +/- 2.1 (P less than 0.02), and 14.8 +/- 1.7 (P less than 0.02) mmHg, respectively. The pyloric pressure responses to insulin hypoglycemia, duodenal acidification, and intraduodenal olive oil were 11.3 +/- 1.5, 13.4 +/- 1.4, and 11.3 +/- 1.4 mmHg, respectively. The serum concentrations of immunoreactive glucagon during infusion of the lowest active dosage of glucagon and insulin hypoglycemia were 801 +/- 55 and 322 +/- 12 pg/ml, respectively. The serum concentrations of immunoreactive secretin during infusion of the lowest active dosage of secretin and during duodenal acidification were 980 +/- 60 and 110 +/- 7.0 pg/ml, respectively. Although pyloric contraction can be induced by administration of exogenous glucagon, secretin, and cholecystokinin, these studies suggest that these effects may have no physiological relevance.