Pancreatic secretion after selective and truncal vagotomy in the dog

Abstract

External pancreatic secretion was studied in 4 dogs: 2 with a Thomas cannula and 2 with a new cannula in which a duodenal pouch acts as an extension of the pancreatic duct. Peak bicarbonate outputs after a meal were about a third of the maximal secretory capacity of the pancreas in response to single intravenous injections of pure secretin, whereas peak protein concentrations and outputs after a meal were of the order of the maximum response to injections of secretin and pancreozymin. There were no consistent changes in hormonestimulated pancreatic secretion after selective vagotomy. Meal‐stimulated pancreatic secretion was markedly reduced after truncal vagotomy (81 per cent reduction in peak bicarbonate output, 65 per cent in peak protein output). Secretin‐stimulated bicarbonate output was markedly decreased 3 weeks after truncal vagotomy, but then gradually increased to control values, and in 1 dog to twice the control. Pancreozymin‐stimulated protein output was increased after truncal vagotomy, reaching values two to three times the control. Local anaesthetics applied topically to the periampullary duodenal mucosa markedly inhibited secretin‐stimulated bicarbonate output even after truncal vagotomy, but there was only slight reduction after subcutaneous lignocaine. The reduction in food‐stimulated pancreatic secretion after truncal vagotomy is unlikely to be caused by pancreatic denervation, since the postvagotomy pancreatic response to direct stimulation with exogenous hormones is normal or supranormal, and is probably due to decreased release of gastrointestinal hormones after a meal. Local reflex arcs may influence the pancreas and may explain (by denervation supersensitivity) the post‐vagotomy increase in pancreatic secretion as well as the effects of topical local anaesthetics. The role of neural factors in the regulation of external pancreatic secretion has long been disputed. This subject is now of particular clinical interest in relation to the causes of post‐vagotomy diarrhoea and steatorrhoea (for a review of the literature, see Cox, 1969). With the development of a new cannula for studying external pancreatic secretion in the unanaesthetized dog (Thambugala, 1971) the opportunity was taken to study the effects of selective and truncal vagotomy on the pancreatic secretory responses to food and pure secretin and pancreozymin.