Primary Action of Secretin in the Digestive System
Secretin primarily stimulates pancreatic bicarbonate secretion, not enzyme secretion, making option (b) incorrect. 1, 2
Secretin's Effects on Pancreatic Secretion
- Secretin is a hormone released from duodenal S-cells postprandially that primarily stimulates pancreatic bicarbonate secretion, which helps neutralize acidic chyme entering the duodenum 1
- While secretin can stimulate pancreatic enzyme secretion at high (pharmacological) doses, this is not its primary physiological action 1, 2
- At physiological concentrations, secretin does not significantly stimulate pancreatic enzyme secretion, which is primarily regulated by cholecystokinin (CCK) 3, 4
Effects on Gastric Function
- Secretin inhibits gastric acid secretion, not stimulates it, making option (d) incorrect 4
- Secretin delays gastric emptying, which helps optimize the digestion process by allowing more time for proper digestion and absorption 4, 5
Effects on Intestinal Motility
- Secretin contributes to the regulation of gastrointestinal motility, but its primary effect is not inhibition of intestinal motility, making option (c) incorrect 4
- The coordination of motility with intestinal transit of chyme involves multiple hormones, with secretin playing a role in the integrated gastrointestinal secretory and motor responses 6
Effects on Gastrin Secretion
- Secretin does not stimulate gastrin secretion, making option (a) incorrect 3
- In fact, secretin can inhibit gastrin release as part of the regulatory mechanisms controlling gastric acid secretion 4
Regulatory Mechanisms Involving Secretin
- Secretin release and action are mediated through neurohormonal interactions involving the vagus nerve and multiple regulatory peptides 3, 4
- The action of secretin in the pancreas depends on insulin, which suppresses local release of inhibitory hormones like somatostatin and pancreatic polypeptide 4
- Secretin works synergistically with CCK to regulate pancreatic secretion, with CCK primarily stimulating enzyme secretion while secretin primarily stimulates bicarbonate and fluid secretion 3
Clinical Significance
- Synthetic human secretin is used clinically for studies of exocrine pancreatic secretion and for secretin-enhanced magnetic resonance cholangiopancreatography 4
- Secretin also has potential therapeutic use for relief of severe pain in chronic pancreatitis 4
- Recent research suggests secretin may also function as an anorectic peptide, potentially playing a role in appetite control through the melanocortin system 5