Effect of atropine on secretion from intact and transplanted pancreas in dog.

In dogs with a fistula of the intact pancreas and a transplanted portion of pancreas, we studied the effect of atropine on the pancreatic secretory response to intravenous caerulein and to intestinal perfusion with tryptophan, both given with a secretin background. Atropine (50 micrograms . kg-1 given as an intravenous bolus injection followed by 20 micrograms . kg-1 . h-1 iv infusion) depressed bicarbonate and protein secretion from intact pancreas during stimulation by secretin alone (250 ng . kg-1 . h-1) but did not suppress the increment in bicarbonate secretion in response to caerulein or tryptophan given against the secretin background. In intact pancreas, atropine suppressed protein secretion in response to tryptophan but not in response to caerulein. Atropine had no significant effect on the secretion of bicarbonate and protein from transplanted pancreas in response to secretin, caerulein, or tryptophan. Thus, the only significant effect of atropine on bicarbonate and protein secretion from intact and transplanted pancreas in response to intravenous caerulein or intraduodenal tryptophan, both given against a background of secretin, was inhibition of the protein response to tryptophan in the intact pancreas. These findings are compatible with the hypothesis that pancreatic protein secretion in response to intraduodenal tryptophan is mediated in part by a cholinergic enteropancreatic reflex.