Adrenergic modulation of interdigestive pancreatic secretion in humans

Whether the adrenergic pathways participate in the control of interdigestive pancreatic function in humans is uncertain. To determine if changes in alpha- or beta-adrenergic tone modulate interdigestive pancreatic enzyme output, 16 healthy subjects were intubated with an orojejunal tube to collect and quantify pancreatic trypsin secretion and record motility. After observation of a complete interdigestive cycle (control period), eight groups of two subjects each received 2-hour intravenous infusions of the alpha- and beta-agonist epinephrine (50 ng.kg-1.min-1), the alpha-antagonist phentolamine (5 mg/2 min followed by 500 micrograms/min), the beta-antagonist propranolol (5 mg/2 min followed by 80 micrograms/min), or saline as control, alone or in combination. Drugs were assigned in a random mode according to a 2(3) factorial design. Analysis of variance showed that epinephrine decreased trypsin output by 43% (P less than 0.05). By contrast, trypsin output was increased fourfold in the presence of phentolamine (P less than 0.01), whereas propranolol had no effect. These data suggest that an inhibitory alpha-adrenergic tone modulates human interdigestive pancreatic enzyme secretion whereas beta inputs are less important.