Stimulation of human pancreatic polypeptide and gastrin by Boots and GIH secretin: in vitro and in vivo studies.

We have studied the concentration of various gastrointestinal peptides in a crude porcine secretin (Boots) preparation and pure natural porcine secretin (GIH, Kabi) preparation. Boots secretin was found to contain 140.3 ng secretin, 1.27 ng human pancreatic polypeptide (hPP), 1.03 ng gastrin, 137.4 ng cholecystokinin (CCK), 241 microU insulin, 1.86 ng vasoactive intestinal polypeptide (VIP), 2.22 ng glucagon and 6.60 ng somatostatin (SRIF) per Crick Harper unit Boots secretin. Sephadex gel filtration demonstrated that the immunoreactivity was due to the hormone per se. GIH secretin contained 240 ng secretin per clinical unit (CU) and less than detectable concentrations of hPP, gastrin, CCK, insulin, VIP, glucagon and SRIF. To determine the clinical significance of having contaminating peptides in Boots secretin, we investigated the effect(s) in 4 subjects. Determined in a highly gastrin-specific assay, the mean plasma gastrin response to Boots secretin administration was slightly, but not significantly greater than the GIH secretin response at 1 and 2.5 minutes. However, in some subjects false positive elevations in plasma gastrin immunoreactivity occurred when some commercially available kit gastrin assays were employed. After intravenous injection of Boots secretin, mean plasma hPP levels rose significantly more than after GIH secretin administration. The mean peak plasma insulin level after GIH secretin administration was significantly higher than after Boots secretin. Neither secretin preparation caused a change in plasma glucose, glucagon and SRIF levels. From these results, it is suggested that GIH secretin be used as the preparation of choice in provocative testing for diagnosing gastrinoma or deficiencies of exocrine pancreatic function.