Pancreatic exocrine secretion and immunoreactive secretin release after intraduodenal instillation of 1-phenyl-1-hydroxy-n-pentane and HCl in rats

Portal plasma immunoreactive secretin (IRS) concentrations, pancreatic juice flow, and amylase output were simultaneously measured in response to intraduodenal infusion of 1-phenyl-1-hydroxy-n-pentane (PHP), as well as infusion of hydrochloric acid (HCl). These data were compared with those obtained from intravenous bolus injections of synthetic porcine secretin in anesthetized rats. The intraduodenal infusion of PHP or HCl at a rate of 2 ml/min for 2 min produced a dose-related increase in portal plasma secretin concentrations, pancreatic juice flow, and amylase output. However, the mechanism of secretin release by PHP seems to differ from that of HCl. The secretin response to 0.1 N HCl infused at a rate of 0.1 ml/min for 30 min was complete after 10 min, despite continued infusion, while PHP stimulated a secretin release which persisted for 10 min after cessation of infusion. The pH in the second portion of the duodenum, following PHP infusion, remained consistently greater than 6.3. PHP-stimulated pancreatic exocrine secretions were only partially suppressed by somatostatin, while secretin release was almost completely inhibited. However, intraduodenal PHP may stimulate the release of secretin along with other gastrointestinal hormones, and the endogenous release of these hormones may not be inhibited by somatostatin.