Canine pancreatic juice stimulates the release of secretin and pancreatic secretion in the dog

Multiple actions of secretin in the human body

The discovery of secretin initiated the field of endocrinology. Over the past century, multiple gastrointestinal functions of secretin have been extensively studied, and it was discovered that the principal function of this peptide in the gastrointestinal system is to facilitate digestion and to provide protection. In view of the late identification of secretin and the secretin receptor in various tissues, including the central nervous system, the pleiotropic functions of secretin have more recently been an area of intense focus. Secretin is a classical hormone, and recent studies clearly showed secretin's involvement in neural and neuroendocrine pathways, although the neuroactivity and neural regulation of its release are yet to be elucidated. This chapter reviews our current understanding of the pleiotropic actions of secretin with a special focus on the hormonal and neural interdependent pathways that mediate these actions.

Pancreatic phospholipase A2 from the small intestine is a secretin-releasing factor in rats

A secretin-releasing activity exists in the upper small intestine and pancreatic juice in the rat and the dog. Group I pancreatic phospholipase A2 (PLA2) in canine pancreatic juice and porcine pancreatic PLA2 stimulate the release of secretin from both STC-1 cells and a secretin-producing cell (S cell)-enriched preparation isolated from rat duodenal mucosa. We investigated the distribution and release of pancreatic PLA2-like immunoreactivity in the gastrointestinal tract and the role of PLA2 on the release of secretin and pancreatic exocrine secretion in response to duodenal acidification in anesthetized rats. PLA2-like immunoreactivity was detected in the mucosa throughout the gastrointestinal tract. High concentrations of PLA2 were found in both the small intestine and the pancreas. Duodenal acidification significantly increased the release of PLA2 from the upper small intestine (385% over basal secretion). Intravenous infusion of an anti-PLA2 serum (anti-PLA2) dose-dependently inhibited the release of secretin and pancreatic exocrine secretion in response to duodenal acid perfusion. Preincubation of the concentrate of intestinal acid perfusate (10-fold) from donor rats with the anti-PLA2 significantly suppressed its stimulation of secretin release and pancreatic exocrine secretion in recipient rats. We conclude that pancreatic PLA2 also functions as a secretin-releasing factor in the small intestine that mediates acid-stimulated release of secretin in rats.