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 α-or β-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 α- and β-agonist epinephrine (50 ng · kg^-1 · min^-1), the α-antagonist phentolamine (5 mg/2 min followed by 500 μg/min), the β-antagonist propranolol (5 mg/2 min followed by 80 μg/min), or saline as control, alone or in combination. Drugs were assigned in a random mode according to a 2³ factorial design. Analysis of variance showed that epinephrine decreased trypsin output by 43% (P < 0.05). By contrast, trypsin output was increased fourfold in the presence of phentolamine (P < 0.01), whereas propranolol had no effect. These data suggest that an inhibitory α-adrenergic tone modulates human interdigestive pancreatic enzyme secretion whereas β inputs are less important.